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TEXTBOOK 

I 0011120214 

MEDICAL ENTOMOLOGY 




14 2o J 



WALTER SCOTT PATTON. M.B. (Edin.). I.M.S. 

Membre Correspondanl de la Societe de Pathologic Exotique 

King Institute of Preventive Medicine, Guindy, Madras 
Lately on Special duty for the investigation of Kala 
Azar in Madras and of Oriental Sore in Cambay 

and 

FRANCIS WILUAM CRAGG. M.D. (Edin.). I.M.S. 

Fellow of the Entomological Society of London 

Central Research Institute, Kasauli, Punjab 
Lately Assistant to the Director, King Institute of 
Preventive Medicine 



CHRISTIAN LITERATURE SOCIETY FOR INDIA 

LONDON, MADRAS AND CALCUTTA 
1913 



[All rights reserved.] 



Digitized by the Internet Archive 

in 2015 



https://archive.org/details/b21351909 



FOREWORD 



Captains Patton and Cragg have asked me to write a Foreword to 
their textbook on Medical Entomology. I have much pleasure in doing 
so, even though the full preface written by the authors leaves me little to 
say and the importance of the subject is so well known that no obiter 
dicta of mine are called for. 

I have watched this book through all its stages and I know perhaps 
better than any one else the enormous labour that has been entailed by 
its preparation. It covers an immense and in many places untrodden 
field : it is moreover thoroughly practical and the greatest care has been 
taken in the description of technique. 

For both these reasons it will be extremely useful to all workers in 
Medical Entomology, and I trust that it will meet with the success 
which it undoubtedly deserves. 

With these few remarks I leave the book to speak for itself. 



Delhi, 




November 



C. P. LUKIS, 



Director-General, 
Indian Medical Service. 



PREFACE 



One of the worst difficulties, which the medical and veterinary officer 
practising in the tropics has to contend with, is that of obtaining 
the necessary literature, and there is perhaps no subject in which 
this difficulty has been more felt than in applied entomology. The 
many excellent textbooks on general entomology are of little service, 
as they do not deal with the practical applications of the subject to 
sanitation, or with the particular forms with which the medical officer 
is concerned ,* the special papers, with the exception of those of the 
last three or four years, are scattered in a hundred different journals, 
to few of which the worker abroad can have access. With the advent 
of journals specially devoted to the subject the current literature has 
now become available, and it is possible to keep one's knowledge up 
to date without an undue expenditure of time or money, but the 
difficulty regarding the older work, much of which is of a very high 
order, remains the same. Many important papers are not to be found 
outside the larger libraries, or can only be purchased rarely and at a 
high price. 

It is particularly with regard to the practical points which come 
up. in the course of experiments — such as any medical officer may be 
called upon to carry out before practical sanitary measures directed 
against the insect carriers of disease can be adopted — that the isolated 
worker finds himself at a loss. Detailed accounts of the methods 
employed in breeding and manipulating insects and ticks in the labora- 
tory, or of the internal anatomy of disease-bearing forms, are only 
to be obtained, if at all, by a search through a very large mass of 
literature in many languages. In too many cases the writers of papers 
confine themselves to a discussion of results, omitting altogether or 
giving only a brief note on the methods by which these have been 
obtained, and assuming a knowledge of the internal structures of 
insects which the ordinary medical man cannot fairly be expected to 
possess. In very many instances, even among the more familiar 
insects, information of the particular sort which is required for the 
successful carrying out of experiments is not to be found in any 
publication. We know of no account, for instance, of a method of 



VI 



PREFACE 



breeding the house fly which is suitable for use in tropical countries ; 
the only account of the anatomy of the body louse is so rare that 
we have not, after two years' negotiations with book-sellers, succeeded 
in obtaining a copy. 

Our object in writing this textbook has been to supply the needs 
of our fellow-workers in these respects as far as possible ; to compile, 
in fact, a guide to the study of the relations between arthropods and 
disease, rather than a textbook on entomology. The general plan 
of the work has been suggested by the difficulties with which we 
ourselves have had to contend, and by the questions which have been 
asked us by visitors to our laboratory. In so ill-defined a subject 
it has often been difficult to decide what to include and what to 
omit ; a work of this nature cannot hope to be complete, and, although 
the book has grown in the making to be considerably larger than 
what was at first projected, it has been found necessary to exclude 
many forms of interest. At the same time it has been recognized that 
too close limitation to forms of known importance would be dis- 
advantageous. In this subject, as in any other, a certain breadth of 
view is essential to progress, and one has to remember that advance 
has depended in the past, and will assuredly depend in the future, 
to a large extent upon the study of non-pathogenic organisms, and 
the subsequent application of the results so obtained to the study 
of the related pathogenic forms. Very many blood-sucking arthropods 
which have, so far as we know at present, no connection with disease 
have been dealt with, and for a similar reason special prominence 
has been given to forms which act as the invertebrate hosts of the 
non-pathogenic ' natural ' parasites. 

In the arrangement of the matter a regular sequence has been observ- 
ed as far as possible, the general features of the group, its relation to 
disease and its natural parasites, external anatomy, classification and 
description of species, bionomics and breeding habits, methods of breed- 
ing and laboratory manipulation, internal anatomy and methods of dis- 
section, being discussed in turn, concluding with a list of papers dealing 
with the group. To this rule there are a few exceptions. The second 
chapter, dealing with the anatomy of the Diptera, is intended to serve 
as an introduction to insect morphology, and matters discussed at length 
therein arc not referred to again in the anatomical portions of the sub- 
sequent chapters ; the reader who has no previous experience of this kind 
of work is recommended, even if he proposes to experiment with insects 
of another order, to read this chapter first and to make himself 



PREFACE 



vn 



familiar with the various organs by dissection of a few common types. 
As far as possible those Diptera which are of practical importance 
have been selected as examples for description and illustration, so 
that, with the aid of the index, the chapter will also serve as a guide 
to these forms. In the eleventh chapter practical laboratory methods, 
which apply equally to any order of insects and to ticks, are dealt 
with. It is not intended, of course, to provide a guide to laboratory 
technique, but merely to indicate the deviations from the ordinary 
methods which are necessary in dealing with insect tissues. It is not 
claimed that the methods advocated are the ideal ones, but they are 
those which have resulted from our own experience, and are, like most 
practical methods, the outcome of mistakes and misfortunes. 

The external anatomy of the different groups, perhaps a very dry 
subject, has been dealt with at some length. The reason for this is 
that, rightly or wrongly, classification is founded almost entirely upon 
external features, and unless the student has some familiarity with 
these it is impossible for him to follow the systems of classification 
or to use the keys for the identification of species. In most cases the 
terminology used by authorities in systematic work has been retained, 
even if it is probably incorrect morphologically. For instance, the 
terminology of the thorax of the mosquito as used by Theobald is not 
altered either in the keys or descriptions, although, as was pointed 
out some years ago by Nuttall and Shipley, it is not in accordance 
with the anatomy of the parts ; similarly, the organ of the louse, 
termed by Enderlein the pharynx, is referred to by that name in the 
keys and descriptions taken from his work, although, as pointed out 
in the account of the anatomy of that insect, it does not correspond 
to the pharynx in other orders. It is not possible to ensure finality 
in such matters, and the old terms are retained to avoid confusion. 

In classification the system of an authority in each group has 
been followed ; where there are several to choose from, the selection 
of one is to be taken as indicating merely a slight preference, and 
does not imply a belief on our part that the alternative systerhs 
are incorrect. For practical purposes one is often as good as another, 
and only future research can show which will present the most natural 
grouping. Such matters, we believe, can well be left to the specialist. 

Free use has been made of the keys to the genera and species 
which have been compiled by specialists. Such keys, and partic- 
ularly those which include only the species of a given locality, are of 
the greatest service" to the isolated worker who has no type collection 



viii PREFACE 

to refer to, and we feel that no further justification for reproducing 
them is necessary, than that they will become more accessible to those 
who have the most need of them. At present hardly a dozen of 
those in the text have appeared in journals which circulate in the 
tropics, and many have not appeared at all in the English language. 

In accordance with the main object of the book, particular attention 
has been paid to the description of methods of breeding and laboratory 
manipulation. The methods which are given are, in the great majority 
of cases, those which we have used ourselves at the King Institute. 
It is not claimed that they are the only methods, or indeed the ideal 
ones, but they have all stood the test of experience, and have been 
successful in our hands. Where the methods of other workers are 
described they have been repeated by us in every case in which it could 
be done. We are only too well aware what an enormous amount of 
time may be wasted in finding out simple points of technique. 

The sections on internal anatomy also contain a large amount of 
original matter. With few exceptions the descriptions have been writ- 
ten and the figures drawn from dissections and sections prepared for 
the purpose. 

In the list of publications at the end of each chapter, those which 
include full references to previous work, and those which describe 
experimental methods, have been specially included. In addition, papers 
quoted in the text, and those to which we are specially indebted for 
information, are quoted. It is hoped that the short lists given will 
sufiice to guide the reader to the literature on the subject when a library 
is available. 

Of the incompleteness and the many imperfections of our work we 
are well aware, now that it is concluded. We feel, however, that 
we may justly ask some indulgence if we have omitted points of import- 
ance, or if the work of others has not always received the consideration 
which was due, for the book has been written and printed entirely 
in India, without access to literature othei- than that in our own 
possession and in the library of the Institute. We have also been 
without that friendly advice and criticism from fellow-workers which is 
of so much service in eliminating errors. On the other hand, a rich 
collection of material has always been available in the neighbourhood 
of our laboratory, and if we have failed to make the most of it the blame 
must be ours. 

It is our pleasant duty to offer thanks to those whose aid has made 
our task possible. To Sir Harcourt Butler, head of the Education 



PREFACE ix: 

Department of the Government of India, and to Sir Pardey Lukis, 
Director-General of the Indian Medical Service, we are deepl}' indebted, 
as without their encouragement and assistance the book could not 
have been written. We have also to acknowledge the financial aid 
received from the Indian Research Fund, which has enabled us to 
offer the book at a lower price than would otherwise have been the 
case. The Government of Madras have also rendered us substantial 
assistance. To Surgeon-General Bannerman, of the Government of 
Madras, we are indebted for much kindly encouragement. 

We have to express our thanks to the following authors for the 
permission, so freely accorded us to reproduce illustrations which 
have appeared elsewhere : Dr. Annandale (and also to the Trustees 
of the Indian Museum), for the illustration of the external genitalia 
of Phlehotomus ; Mr. Austen (and the Trustees of the British Museum), 
for the drawings of Glossina palpalis and G. morsitans, Melophagus 
oviniis, and the diagrams of the chaetotaxy of Glossina ; Dr. Gordon 
Hewitt, for two drawings from his monograph on Mtisca domestica ; 
Dr. Graham Smith, for several drawings from his paper on the pro- 
boscis of the Blow Fly ; Professor Miall, for four drawings from his 
and Professor Denny's book on the Cockroach ; Professor Minchin 
and Dr. Roubaud for the drawing of the internal anatomy of Glossina ; 
Dr. Roubaud for the drawings, taken from his thesis, of the rep- 
roductive organs of Glossina ; Professor Neumann, for the drawings 
of some ticks and parts of lice ; Professor Newstead and Mr. Guy 
Marshall, for the drawings of Phlehotomus papatasi and the external 
genitalia of Glossina ; Professor Oswaldo Cruz and Dr. Carlos Chagas 
for the drawing of Conorhinus megistus ; the Hon. N. C. Roths- 
child, for the drawings of the heads of Ctenocephalus canis and 
felis and the manubrium of the former ; Dr. Jordan and Mr. Roths- 
child for the drawings of the external genitalia of Xenopsylla cheopis ; 
and Dr. Wardell Stiles for drawings of the spiracles of some species 
of Dermacentor. We are indebted to Mr. Austen for his kind olBces 
in procuring for us the drawings of Anopheles costalis and funestiis, 
and to Mr. Terzi for the admirable manner in which he has executed 
them. 

In several instances the vagaries of the post have prevented our 
receiving a reply to a request for permission to reproduce ; all draw- 
ings, however, which are taken from other works are duly acknow- 
ledged in the description of the plate on which they occur. We 
would add our thanks to the publishers of the various papers in 

B 



PJiEFACE. 



which the above drawings have appeared. From them, as from the- 
authors, we have met with uniform courtesy. The Director-General 
of the Indian Medical Service, on behalf of the Government of India, 
has permitted us to use the figures on Plates VI, VII, IX, X and 
XII, which have appeared in Memoirs by the junior author, and has 
added further to our indebtedness by allowing us to use the blocks. 
Mr. Hathaway, the publisher of Williston's North American Diptera, 
has permitted us the use of the two figures illustrating chaetotaxy, 
and has assured us that the author would have had no objection 
had it been possible to communicate with him. The publishers of 
the Arbeiten aus dem Kaiserlichen Gesundheitsamte have allowed us to 
reproduce the figure of the proventriculus of Ciilex by Schaudinn, the 
authorities of the Smithsonian Institution the figure of the Muscoidean 
head by Townsend, and the publishers of the American Naturalist 
the figure of Comstock and Needham's 'urotype'. We are indebted 
to the Entomological Society of London for permission to reproduce 
the figure of the divisions of the Dipterous thorax by Professor Mik, 
which- appeared in their Transactions. 

All the line drawings of bugs, lice, ticks and acari and all the brush 
drawings with the exception of those on Plate XXVI and those of 
Haematopota pluvialis, Anopheles costalis and Anopheles funestus, and 
some of the line drawings illustrating the anatomy of ticks, are by 
Mrs. Patton. The extent of our indebtedness to her is difficult to 
express. Any value the book may have is very largely due to her skill 
and to the unremitting care which she lavished on the work. In 
several instances details of structure and marking, not previously noted, 
have been picked out and drawn by her. The remaining drawings 
are the work of the junior author. 

For the preparation of many of the drawings and descriptions it 
has been necessary to obtain specimens of forms not present in our 
neighbourhood, and it gives us great pleasure to be able to return 
thanks to those who have so courteously complied with our requests. 
We are indebted to Dr. Annandale for a large collection of named 
Diptera ; to Professor Bezzi for a large collection of Muscids, includ- 
ing Haematohia and Haematobosca ; to Dr. Anton Breinl for a 
collection of Culicidae and Muscidae from Australia ; to Mr. Nathan 
Banks and Dr. C. Wardell Stiles for several species of American ticks ; 
to Dr. Fantham and Mr. Wigham for specimens of Ornithodorus 
moubata ; to Professor Oswaldo Cruz for specimens of Conorhinus 
tnegistus j to Mr. Hadwen for a collection of ticks from Canada ; to 



PREFACE 



Mr. Hewlett for specimens of Cemtopogon and Simulium ; to Major 
W. Glen Liston, I. M.S., for specimens of Phthinis pubis; to Mr, Guy 
Marshall, Director of the Imperial Bureau of Entomology, for a large 
collection of Diptera, including many specimens of Glossina ; to Professor 
Neumann, to whom we are greatly indebted on several other accounts, 
for a remarkably fine collection of ticks ; to Dr. Nicolle, for a collection 
of Algerian flies ; to Major Perry, I. M.S., for eggs of several species 
of Anopheles, and for imagines ; to Miss Porter, for specimens of 
Melophagus ovinus ; to Dr. Roubaud, for many Muscids, including 
Glossina and Auchmeromyia ; to Dr. Shenkling, for a large collection 
of Muscidae ; to Baron Surcouf, for many species of Musca, including 
Musca corvina ; to Dr. Stanton, for a collection of Stomoxys from the 
Federated Malay States ; and to Dr. Stephens, for specimens of Glossina 
with puparia. 

We are glad to have this opportunity to express our sincere 
thanks to those who, with unfailing courtesy, have helped us for 
several years in the identification of specimens. Our acknowledge- 
ments in this direction are due particularly to Professor Bezzi, Dr. 
Speiser, Professor Neumann, Professor Kieffer, Professor Nuttall, 
Professor Newstead, Dr. Annandale, Mr. Austen, Mr. Brunetti and 
to the Hon. N. C. Rothschild. We are well aware of the amount of time 
and trouble which these gentlemen must have expended on our behalf. 
Mr. Distant and Mr. Nathan Banks have also helped us with advice 
in connection with the chapters on Rhynchota and Acari respectively. 
Our thanks are due to Dr. Gibson for his kindness in taking the 
photographs and for considerable help in translations from the German. 
We are also greatly indebted to Mr. T. Bainbrigge Fletcher who has 
kept us informed of all important papers dealing with Medical Entomo- 
logy ; his extensive knowledge of the literature has been most valuable. 

The junior author wishes to acknowledge the facilities afforded 
him while at home by Professor Cossar Ewart and the staff of the 
Zoological Department of the University of Edinburgh, and in partic- 
ular to acknowledge his indebtedness to Dr. Ashworth for a training 
in technique which has proved of the utmost value. 

Lastly, our thanks are due to our publishers, who have borne with 
exemplary patience our many shortcomings; and to Messrs. Wiele 
and Kleine of Madras for the admirable manner in which they have 
reproduced the plates. 

MADRAS I W. S. P. 

December 1, 1913\ F. W. C. 



CONTENTS 



CHAPTER I 

Entomology as a branch of preventive medicine. Zoological Position of the 
blood-sucking Arthropoda 3. The Order Acarina 5. Geographical 
Distribution. Table of regions 7 . _ . 

CHAPTER II 
Anatomy and Physiology of the Blood-sucking Diptera. 

SECTION 1 

General Structure — chitin 11, — nomenclature of exo-skeleton 12. The Head 
and its regions 13, — eyes — antennae 16, — mouth parts and sucking ap- 
paratus 19,— their main features in the Diptera — Tabanus as a type 22, — 
other Orthorraphic flies 28, — the mosquito 29, — mechanism of the parts 33, 
— mouth parts of Miisca 38,— its pseudotracheal membrane 42, — Genus 
Philaematomyia 48,— the $toinoxys group 51, — Glossina 58, — Hippobosca 
62, — internal structure of the head 66, — the neck 67. The Thorax 68, — 
Tabanus, Cttlex, Stomoxys — nomenclature of the thorax 76, — the wings 
77, — systems of venation 78, — the legs 84. The Abdomen 85, — external 
genitalia, Phlebotoinus 86, Glossina 88, Musca, 89. Chaetotaxy, 90. 
(Plates I to XIX) 

SECTION 2 

The Internal Structures. The Muscles 93, — mechanism of flight 95. The 
Respiratory System 96, — spiracles — tracheae and air sacs, their structure 
— mechanism of respiration 99. The Alimentary Canal 100, — development — 
its divisions — alimentary tract of Tabanus as a type 102, — mosquito 109, — 
Cyclorraphic flies 112, — Musca, Philaematomyia, Glossina, Hippobosca . 
The Salivary Apparatus 119, — function of saliva. Digestion and absorption 
of blood 123, — function of mesenteron -significance of the peritrophic 
membrane — secretion and excretion — regeneration of cells. The Heart, 
Vessels, and Pericardial cells 128, — mechanism of the circulation^ the 
haematocoele 129, — the blood 131, — the fat body. The Reproductive 
System 132, — general structure — relations of the sexes — the male organs, 
133, — Culex, Tabanus, Phlebotonius, Musca, Glossina, Hippobosca — the 
female organs 135, — the ovaries — structure of follicles — oviduct — sper- 
mathecae — accessory glands — pupiparous flies 138, — the origin of the pupi- 
parous habit 139, — Musca bezzii 140, — Glossina 141, — the ovaries, uterus, 
spermathecae — milk glands, — Melopliagus 145, — spermatozoa 146. The 
Nervous System 146,— .4no/)/ie/es, Tabanus, Musca. Literature, 148. 
(Plates XX to XXX) 

CHAPTER III 

The Order Diptera, 

SECTION 1 

Orthorrapha — Nematocera. Metamorphosis and early stages 151,— classifi- 
cation of Diptera 155, — Family Chironomidae 157, — Ccratopogon, Culi- 
coides — habits— early stages — breeding technique. Family Simuliidae 165, 
— key's to the Indian and North and South American species— bionomics 



XIV 



CONTENTS 



and early stages — breeding technique. Family Psychodidae 177, — genus 
Phlebotoinus — keys to the Indian, Maltese and South American species — 
bionomics and early stages — breeding technique. Family Culicidae 187,— 
classification — Dixinae 189, — Corethrinae 190, — Culicinae 192, — external and 
internal structure of early stages of mosquitoes — keys to larvae of Indian 
and African Anopheles 204, — classification of Culicinae 205, — key to genera 
of subfamily Culicinae 208, — Culex, Taeniorhynchns, Mansonoides — key 
to common species of Stegomyia 216, — Stegoiityia fasciata — bionomics 
and early stages. The Anophelinae 220, — key to the genera— keys to Indian 
and African Anopheles — descriptions of all the known species of Anopheles 
— bionomics of Anophelinae 255, — breeding habits — seasonal prevalence — 
hibernation — methods of distribution — age composition of Anopheles 
communities — choice of host — some problems in bionomics — breeding 
technique 265, — oviposition in captivity — collection of eggs and larvae — 
identification of larvae — raising of imagines from larvae — methods of 
keeping and feeding mosquitoes — pitfalls in feeding experiments, 270. 
(Plates XXXI to XXXIX) 

SECTION 2 

Orthorrapha — Brachycera. Family Tabanidae271, — classification — keys to 
all the families — -Tabanus 276, — key to the Oriental species — descriptions 
of some Indian species — Chrysops 289, — key to the Oriental species — 
Haeinatopota 291, — Silvius, Cadicera, Pangonia — bionomics of the 
Tabanidae 294, — breeding habits and early stages — external structure of 
larva 299, — alimentary tract — respiratory system — pupa —breeding technique 
303. Family Leptidae, 306, — Phoridae — Aphiochaeta fen'uginea,Asi\ida.e. 
(Plates XL to XLII) . 

CHAPTER IV 
SECTION 1 

C YCLO R RAP HA — Acalypterae 310, — Sepsidae — Cordyluridae — Borboridae — 
Drosophilidae — species infected with flagellates — breeding technique — 
Calypterae 312, — Tachinidae — Sarcophagidae — breeding technique — Oestri- 
dae 315, — classification — key to the genera — oestrid larva 317, — key to 
the oestrid larvae — Gastrophihis, Oestrus, Hypoderma — early stages — 
bot flies of animals — -Dennatobia. Family Muscidae 322, — Calliphorinae 
324, — Calliphora, Lucilia, Pycnosoina, Chrysoinyia — breeding techni- 
que 327, — identification of species causing myiasis — Atichmeromyia 327, — 
bionomics of A. liiteola — structure and habits of larva — Chocromyia — 
Ochroinyia, Bcngalia, Cordylobia — Muscinae 331, — Mmsc«,— Group 1, 
non-blood-sucking species, including house flies 333. Descriptions of dotnes- 
tica, ncbulo, entoniata, detcnninata, august if rons — early stages ol Miisca 
337, — breeding habits — house flies as carriers of disease 338, — breeding 
technique 342, — house flies which may be mistaken for Musca 346, — Group 
2 — importance of the blood-sucking non-biting species of Musca 348, — de- 
scriptions oi pattoni, gibsoni, convexiffons, nigrithorax, bezzii, corvina 
ovipara, corvina vivipara — breeding technique 354. The Biting Muscidae 
355, — Philaematoniyia — descriptions of lincata, insignis, a,nd gurnei — bio- 
nomics and early stages of insignis 358, — Stomoxydinae 360, — key to the 
genera— Stoiiioxys — identification of species — key to Oriental species 362, — 
Stombxys ' calcltrans — relation to disease — bionomics 363,— life history 
— breeding technique 367, — methods employed in keeping and feeding 
Stomoxys — Hactnatobia, Bdellolarynx, Hacniatobosca , Stygeromyia — 
Lyperosia 372, — key to common species of Lyperosia — iiiinuta, irritans 
and exigua — bionomics 375, — breeding habits and early stages — breeding 
technique — Glossininae 376, — classification — key to the species 378, — Glos- 
sina palpalis 380, — Geographical distribution — habitat and habits in repro- 
duction 385, — intra-uterine development — structure of larva 387, — pupation 
— number of larvae produced — effects of humidity and temperature — descrip- 
tions of other species 391, — Clossina ntorsitans, — bionomics, etc. 397, — 
breeding technique, 401. (Plates XLIII to LI) 



CQNTENTS 



XV 



SECTION 2 PAGE 

The PUPIPARA 404, — classification — Hippoboscidae, 405 — classification — Lyn- 
ch ia — Hippobosca — Lipopteiia — Melopliagus 409, — Nycteribiidae 410, — 
Streblidae — keys to the genera. Methods of collecting and preserving 
Diptera 411, — apparatus — collecting box 415, — mounting flies. Methods of 
dissecting the Diptera, 419. Important literature relating to Diptera, 424, 
(Plate LII) 404 



CHAPTER V 

SiPHONAPTERA, or FLEAS. Position of the group — relation to disease — plague 
and Kala Azar — natural parasites 435. External anatomy 436, — Ctenoce- 
phalus felis — head — antennae — mouth parts 438, — mechanism of mouth 
parts 441, — thorax — abdomen — external genitalia — vestiture 445. Classifica- 
tion 446, — Sarcopsyllidae — the ' Jigger ' flea 448, — other genera. Pulicidae 
450, — key to genera — Piilex 452, — Xenopsylla 453, — key to the species — 
other genera, 455. Life history and early stages of Ctenocephalus fclis 458, — 
anatomy of larva 459, — its food — the pupa. Relation to host 461, — method 
of feeding — fleas found on rats 463, — seasonal prevalence — length of life 
465, — bionomics. Methods of breeding in the laboratory 467, — cages — 
manipulation of single fleas 468, — the ' circus ' flea method. Internal anatomy 
469, — alimentary canal — salivary glands — reproductive system 471, — nervous 
system — dissection, 473. Collection and preservation 474, — identification, 
475. Literature, 475. (Plates LIII to LVIII) 434 



CHAPTER VI 

The Rhynchota, or Bugs. Relation to disease 478, — plague — leprosy— Kala 
Azar — trypanosomiasis. External anatomy, 480. Classification of the Rhyn- 
chota 482, — bugs infected with flagellates. Pentatomidae 484, — Lygaeidae — 
Coreidae. Blood-sucking Bugs — Family Reduviidae 485, — Genus Conor- 
hiniis {Triatoma) — riiirofasciatits 487,-Trelation to disease — bionomics 
and early stages — megistns 492, — relation to disease — bionomics and early 
stages — short descriptions of nine other species, 493. Internal Anatomy — 
dissection of rtibrofasciatus, 496. Family Cimicidae 498, — genera Ciniex, 
Oeciacus, Cacodmus, Haematosiphon and Loxaspis. External Anatomy of 
Cimex rotundatus, 499. Cimex lectulantis and C. rotiindatiis 505, — ■ 
bionomics and early stages — other species — Polyctenidae — species of, 513. 
Internal Anatomy 513, — alimentary tract — sucking pump 514, — salivary ap- 
paratus—reproductive system 518, — organ of Berlese 520, — copulation — stink 
apparatus. Method of dissecting Cimex, 524. Literature, 525. (Plates LIX 
to LXV) 478 

CHAPTER VII 

ANOplura, or Lice. Relations to other orders — relation to disease 528, — 
typhus and relapsing fever — natural parasites. External anatomy 529, — the 
head — mouth parts and sucking apparatus 531, — proboscis and its sheath — 
mechanism of the apparatus. Thorax 539, — legs — abdomen — external geni- 
talia, 540. Classification of Enderlein — key to the genera, 542. Pediculidae 
544, — Genus Pediculus — Neumann's views on Pediciiliis species, 545. 
Haematopinidae 547, — Haematopiniis— s^ecieslound on bovines 549,— other 
genera. Habits, life history and bionomics of P. vestiinenti , 551. Methods 
of breeding in the laboratory — methods of performing transmission experi- 
ments with head and body lice. Internal anatomy of P. vestiinenti 556, — 
alimentary canal — salivary glands — reproductive organs, 559, Methods of 
dissection, 561. Literature, 563. (Plates LXVI to LXXI) .... 527 



CHAPTER VIII 



Order Acarina ; Ixodidae or Ticks. General structure, 565. Classification 
of Acarina, 567. Ixodidae 568,— position of the group — relation to disease 



XVI 



CONTENTS 



568, — natural parasites. External Anatomy 570, — capitulum — palps — mandi- 
bles 572, — hypostome — scutum — porose areas — grooves 574, — genital aper- 
ture — anal orifice — plates, shields and caudal appendage — legs — Haller's 
organ — spiracle, 576. Classification of Ixodidae, 577. Argatini 579, — 
Genus Argas — Neumann's key to the species 580, — reflexus, persicus 
and vespertilionis — hionomics — Genus Ornithodorus 584, — Neumann's key 
to the species — savignyi — bionomics and early stages 586, — moiibata — 
bionomics — relation to disease, 589. Ixodini 589, — Neumann's classification 
— Ixodaria 590, — classification — Genus Ixodes — key to the species 591, — 
ricinus, angiistns — Genus Ceratixodes 595, — Genus Eschatocephalus 596, 
— bionomics of Ixodaria 597. Rhipicephalaria 597, — Genus Rhipicephahis 
— Neumann's key to the species 598, — sanguineus, appendiculatus, siinus, 
bursa, capensis, evertsi — bionomics 605, — Genus Margaropus 606, — 
Neumann's key to the species — annulatns, lounsburyi — bionomics 608, — 
Genus //_)'a/o;»H;a 609, — key to the species — bionomics 610. Amblyomma- 
taria 611, — Neumann's key to the genera — Genus Amblyomnta 611, — 
Neumann's key to the species — hebfaeiini , aniericanuni — bionomics 621, — 
Genus Aponoiniiia 622, — Neumann's key to the species — gervaisi — Genus 
Dennacentor 624, — Neumann's key to the species — andersoni, reticulatus 
— bionomics 627, — Genus Haeniaphysalis 627, — Neumann's key to the 
species — concinna, birmaniae, punctata — bionomics 631. Identification 
of ticks, 633. Breeding and manipulation of ticks for experimental pur- 
poses, 634. Internal Anatomy 651, — dissection — alimentary canal 654, — 
mid-, hind- and fore-intestine — malpighian tubes 658, — buccal cavity 659, — • 
mechanism of mouth parts — pharynx 662, — oesophagus — histology of ali- 
mentary canal — digestion 663, — coxal gland — Gene's organ 665, — stigmal 
plate 666, — tracheae — heart and vessels 668, — nervous system — connective 
tissue and fat body — integument 669, — muscular system — reproductive 
system, female organs 670, male 672, — spermatophore — copulation 673, — 
parthenogenesis 674. Collection and preservation 674, — method of 
removing ticks — keeping live ticks 676, — identification 677. Literature, 
677. (Plates LXXII to LXXXVI) 



CHAPTER IX 

The Order Acarina : Acari or Mites. Relation to disease, 681. Family 
Gamasidae, 681. External and internal anatomy of Laelaps, 682. Classi- 
fication 685, — Subfamily Dermanyssinae — Pteroptus, Dcrinanyssus, Pneu- 
nionyssiis — Subfamily Uropodinae — Subfamily Gamasinae 688, — Laelaps — 
species on rats 689. Family Trombidiidae. Family Hydrachniidae 690. 
Family Sarcoptidae 690, — key to subfamilies — Subfamily Tarsoneminae — 
Subfamily Tyroglyphinae — Subfamily Sarcoptinae 692, — key to genera — 
Genus Sarcoptes 693, — scabei — life history 694, — Genus Psoroptcs — Genus 
Chorioptes. Family Eriophyidae. Family Demodicidae 695, — Demodex 
folliculoruin . Collection and preservation 696, — dissection. Literature, 
696. (Plates LXXXVII and LXXXVIII) 



CHAPTER X 

SECTION 1 

The Order Pentastomida : Linguatulidae or Tongue Worms. Biologi- 
cal position — relation to disease 698. External Anatomy 699, — general 
structure — -mouth parts. Classification 700. Genus Linguatula—serrata 
700, — life history ~ Porocephalus — moniliformis, annillatus, crotali, 
pattoni. Internal Anatomy 701, — salivary glands — reproductive organs, 
female and male. Dissection, 703. Collection and preservation, 703. 
Literature, 704. (Plate LXXXIX) 



CONTENTS xvil 



PAGE 

SECTION 2 

Order Eucopepoda : Cyclops or Water Fleas. Genus Cyclops 705, — 
relation to disease — development of Dracunculus medinensis in Cyclops 
706. External and internal anatomy. Life history and bionomics, 709. 
Literature, 709 705 



CHAPTER XI 

Laboratory Technique. The dissecting microscope 711. Method of making 
cleared preparations 712, — dissection of fresh material 714, — needles — 
method of sharpening needles — technique of dissection 715, — saline solution 
— Perry's bile method 717. Permanent stained preparations of dissections 
— staining with haematoxylin and borax carmine — section cutting — special 
precautions with insect tissues— fixation of sections to the slide. The com- 
bined paraffin and celloidin method — razors, method of sharpening, 724. 



The examination of the tissues for parasites, 726 ...... 711 

CHAPTER XII 

The Relations of Arthropoda to their Parasites i . . , . 726 

INDEX • • . . . 747 



C 



« 4 f « 



LIST OF ILLUSTRATIONS 



Plate Facing Page 

I. Fig. 1. Head of Muscid fly from the front. 

Head of Muscid fly from behind. 
Diagram of insect segmentation. 
Ocellar triangle of Musca. 
Section through chitinous integument. 
Head of male Tabantis from the front ... 11 
Reference letters, Plates I to VII ... 11 

II. Fig. 1. Antenna of Musca nebitlo. 

„ of Glossina submorsitans. 
,, of Hippobosca maculata, 
„ of Culex fatigans, male. 
,, of Chrysops dispar. 
„ of Lyperosia minuta. 

of Tabanus albimedius ... 17 

III. Fig. 1. Head of Muscoidean fly, from the front. 
Facets of compound eye of Tabanus. 
Head of Haemafopota pltivialis, female, 

from the front. 
Scheme of the mouth parts of Orthorraphic 
Diptera. 

Scheme of the sucking apparatus of Orthor- 
raphic Diptera ... ... 21 

IV. Fig. 1. First maxilla of the cockroach. 
Mandible of the cockroach. 
Second maxilla of the cockroach. 
Mouth parts of Haematopota ... 23 

V. Fig. 1. Sucking apparatus of Tabanus. 

Transverse section of head of mosquito. 
Labium of Haematopota. 
Distal end of maxilla of Tabanus. 
Sucking apparatus of mosquito ... 26 

VI. Fig. 1. Hypopharynx of Cefatopogon. 

Labrum-epipharynx of Ceratopogon. 
Labrum-epipharynx of Joblotia. 
Hypopharynx of Joblotia. 
Maxilla of Joblotia. 

Labrum-epipharynx of Tabanus albime- 
dius. 

Mandible of Simulium indicum. 
Hypopharynx of Simulium indicum.. 
Labrum-epipharynx of Simulium indicutn< 



Fig. 


1. 


Fig. 


2. 


r Ig. 




Fig. 


4, 


"Ric 
i ig. 




Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


0. 


Fig. 


7 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


l^ig. 


A 

'T. 


i^ig. 


c 

J. 


TI*i Cf 

r ig. 


1 

1 . 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


7. 


Fig. 


8. 


Fig. 


9. 



XX 



LIST OF ILLUSTRATIONS 



Plate Facing Page 

Fig. 10. Maxilla of Similium indicum. 
Fig. 11. l^abium of Phlebotomus papatasi. 
Fig. 12. Mandible of Phlebotomus papatasi, distal 
end. 

Fig. 13. Maxills. of Phlebotomus papatasi. 
Fig. 14. Mandible of Phlebotomus papatasi. 
Fig. 15. Maxilla, of Phlebotomus papatasi, showing 
the apodeme. 

Fig. 16. L.ahrum-epipharynx of Phlebotomus papa- 
tasi. 

Fig. 17. Hypopharynx of Phlebotomus papatasi. 

Fig. 18. Head of Phlebotomus, side view ... 29 

VII. Fig. 1. Head and proboscis of CwZe^ /a^igaws. 
Fig. 2. Distal end of maxilla of Culex. 
Fig. 3. Distal end of mandible of Culex. 
Fig. 4. Cross-section of proboscis of Culex. 
Fig. 5. Mandible and maxilla of Culex ... 32 

Reference letters, Plates VII to XIII ... 32 

VIII. Fig. 1. Proboscis of Musca nebulo. 

Fig. 2. Isolated pseudotracheal rings. 
Fig. 3. Pseudotracheal ring in situ. 
Fig. 4. Pseudotracheal channels seen from free 
surface. 

Fig. 5. Prestomal teeth of Philaematomyia gur- 
nei. 

Fig. 6. Distal end of labial gutter of Philaema- 
tomyia insignis. 

Fig. 7. Labella of Lyperosia minuta, in position 
of action. 

Fig. 8. Teeth and connected structures of Philae- 
matomyia insignis ... ... 38 

IX. Fig. 1. Labrum-epipharynx of Musca nebulo. 
Fig. 2. Prestomal teeth and pseudotracheal chan- 
nels of Musca convexifrons. 

Fig. 3. Prestomal teeth of Musca pattoni. 

Fig. 4. Mentum and furca of Musca nebulo. 

Fig. 5. Labella of Musca domestica, showing 
prestomal teeth. 

Fig. 6. Discal sclerite of Philaematomyia insig- 
nis. 

Fig. 7. Proboscis of Philaematomyia gurnei. 

Fig. 8. Anterior wall of haustellum of Musca 
nebulo, with discal sclerite and hypo- 
pharynx ... ... ... 44 

X. Fig. 1. Proboscis of Philaematomyia insignis. 
Fig. 2. Section through the lower part of pro- 
boscis of Philaematomyia insignis. 

Fig. 3. Section through the lower end of pro- 
boscis of Lyperosia minuta. 



) 



LIST OF ILLUSTRATIONS 



XXI 



Plate 





Fig. 


4 

T. 


^fi^'^"l/^Tl i"nV/~iniTrn ^T^c^'f^^TY^ of J-jJi'ii/70i^/Tf/^- 








Triyt'Ci' i'ft'jt'QrCt'i> ... ••• 


XI. 


Fig. 


1. 


Proboscis of Stomoxys calcitrans. 




Fig. 


2.' 


Proboscis of Glossina stibmorsitans. 




Fig. 


3. 


Proboscis or Hippobosca maculata 


XII. 


Fig. 


1. 


Labella of Haeinatobia stimulans. 




Fig. 


2. 


Discal sclerite of Pliilaematomyia lineata. 




Fig. 


3. 


Discal sclerite and end of labial gutter of 






Stomoxys calcitrans. 




Fig. 


4. 


Lower end of pharnyx of Haematobia 






stimulans. 




Fig. 


5. 


Isolated tooth of Haematobia stimulans . . . 


XIII. 


Fief. 


1. 


Section through narrow end of proboscis 








of Hippobosca. 




Fief. 


2. 


Section through buccal cavity of Hippo- 








bosca. 






3. 


Proboscis and sucking apparatus of Hippo- 








bosca. 




Fig. 


4. 


Teeth on the labella of Hippobosca. 




Fig. 


5. 


Distal end of proboscis of Hippobosca. 




Fig. 


6. 


Articulation of fulcrum of Hippobosca. 




Fig. 


7. 


Distal end of proboscis of Lyperosia 








minuta. 




■Rice 
r Ig. 


Q 
O. 










ucnmci. 




r ig. 


Q 


inner wan oi laDciict oi \jiosi>tna ... 


XIV. 


Fig. 


1. 


Exo-skeleton of Culex fatigans. 




Fig. 


2. 


Thorax of Tabanus. 




Fig. 


3. 


Ventral plate of ovipositor of Haemato- 








pota. 




Fig. 


4. 


Dorsal plates of ovipositor of Haematopota 


XV. 


Fig. 


1. 


Thorax of Chrysops dispar, from behind. 




Fig. 


2. 


Halter of Chrysops dispar. 




Fig. 


3. 


Tarsus and foot of Haematopota. 




Fig. 


4. 


Apodeme of meso-thorax of Tabanus. 




Fig. 


5. 


root 01 Culex fattgans. 




Fig. 


D. 


Prosternal region of Haematopota. 




Fig. 


7 


/\ leg snowing ine scgmenis ... 


XVI. 


Fig. 


1. 


Thorax of Stomoxys calcitrans. 




Fig. 


2. 


Scales of ptilinal membrane of Philae- 








matomyia insignis. 




Fig. 


3. 


Thoracic inlet of Stomoxys, from internal 








aspect 


XVII. 


Fig. 


1. 


Comstock and Needham's 'urotype'. 




Fig. 


2. 


Wing of Anopheles. 




Fig. 


3. 


Wing of Haematopota. 




Fig. 


4. 


Wing of Stomoxys. 




Fig. 


5. 


Wing of Glossina 



Facing Page 



50 



55 



58 



63 



69 



72 



75 



82 



xxii 



LIST OF ILLUSTRATIONS 



Plate 



Facing Page 



XVIII. 


Fig. 


1. 


Ovipositor of Musca extended. 




Fig. 


2. 


Distal end oi abdomen oi Htppobosca. 




Fig. 


3. 


Genital armature oi Glossma, Male. 




Fig. 


4. 


External genitalia of Phlebotomus. 




Fig. 


5. 


Genital armature of Tabanns. 




Fig. 


6. 


Superior clasper of Ciilex concolor. 




Fig. 


7. 


lerminal segments of abdomen of Job- 








lotia, female ... 


XIX. 


Fig. 


1. 


Thoracic dorsal bristles. 




Fig. 


2. 


Thorax of Musca domestica, showing chae- 








totaxy. 




Fig. 


3. 


Ihorax ot Glossina palpalts, dorsal view. 




Fig. 


4. 


Thorax of Stomoxys calcitrans, side view. 




Fig. 


5. 


Thorax of Glossma palpalis, side view. 


<- 


Fig. 


6. 


Diagram of parts of thorax. 




Fig. 


7 


Head of Musca dowcstica, S66n from 








above 


XX. 


Fig. 


1. 


Respiratory system of Culex. 




Fig. 


2. 


Section through thorax of Haematopota. 




Fig. 


3. 


Respiratory system of Tabanus. 




Fig. 


4. 


Trachea, to show spiral thread. 




Fig. 


5. 


Anterior thoracic spiracle of Musca. 




Fig. 


6. 


Tracheal sacs supplied by the anterior 








spiracle, Musca 


XXL 


Fig. 


1. 


Alimentary tract of Tabanus. 




Fig. 


2. 


Transverse section through mid-gut of 








Tabanus. 




Fig. 


3. 


Cells of proventriculus of Tabanus. 




Fig. 


4. 


Section through one of the mammillae of 








the proventriculus of Tabanus. 




Fig. 


5. 


Villus from mid-gut of Tabanus. 




Fig. 


6. 


Transverse section through the proventri- 








culus of Tabanus 


XXTT 




1. 


IVTa 1 ni fh 1?* Ti tnnp from T^htrii u <i 




Fief. 


2. 


Malpighian tube in section. 




Fig. 


3. 


Alimentary canal of Culicoides kiejferi. 




Fig. 


4. 


Alimentary canal of Phlebotomus minu- 








tus. 




Fig. 


5. 


Cells from the wall of the hind-gut of 








I abanus. 




Fig. 


6. 


Section through the rectum of Tabanus. 




Fig. 


7. 


Section through the oesophagus of Culex, 








anterior end. 




Fig. 


8. 


Section through the oesophagus of Culex, 








posterior end ... 


XXIII. 


Fig. 


1. 


Alimentary tract of Ctilex. 




Fig. 


2. 


Cells from the mid-gut of Culex. 




Fig, 


3. 


Mid-gut of Culex distended with blood. 



87 



91 



98 



104 



109 



LIST OF ILLUSTRATIOjStS 



xxiii 



Plate 



Fig. 
Fig. 



Fig. 
Fig. 



XXIV. Fig. 1. 

Fig. 2. 

Fig. 3. 

Fig. 4. 

Fig. 5. 

Fig. 6. 

Fig. 7. 

Fig. 8. 

XXV. Fig. 1. 

Fig. 2. 



Fig. 5. 

Fig. 6. 

XXVI. Fig. 1. 

Fig. 2. 

XXVII. Fig. 1. 

Fig. 2. 

Fig. 3. 

Fig. 4. 

Fig. 5. 

Fig. 6. 

Fig. 7. 

Fig. 8. 

Fig. 9. 

Fig, 10. 

«>o Fig. 11. 

XXVIII. Fig. 1. 

Fig. 2. 



Facing Page 

Mid-gut of Ciilex, as seen in a routine 
dissection. 

Schematic longitudinal section through 
commencement of mid-gut of Culex ... Ill 

Alimentary tract of Philaematomyia in- 
s ignis. 

Longitudinal section through the proven- 
triculus of PJiilaematoinyia. 

Cells from the hind-gut of Philaema- 
tomyia. 

Diagramatic transverse section showing 

position of peritrophic membrane. 
Diagramatic longitudinal section showing 

the position of the peritrophic membrane. 
Distal end of the malpighian tube of 

Philaematomyia. 
Proximal end of the malpighian tube of 

Philaematomyia. 
AHmentary tract of G/ossma ... 116 

Hind-gut of Hippobosca maculata. 
Transverse section through posterior part 

of abdomen of Haematopota pluvialis. 
Cells from the mid-gut of Philaematomyia. 
Cells from the middle portion of the gut of 

Philaematomyia. 
Longitudinal section through abdomen of 

Philae matomy ia. 
Rectum of Mj«ccr ... ... 118 

Villus of the mid-gut of Tabanus, during 
digestion. 

Villus of the mid-gut of Tabanus, during 
digestion as seen at a lower level ... 125 

Nervous system of Tabanus. 

Pericardial cells from Haematopota. 

Fat body from Philaematomyia. 

Compound thoracic ganglion from Musca. 

Salivary gland of Haematopota, in trans- 
verse section. 

Longitudinal section through the salivary 
gland of Culex. 

Salivary gland of Culex fatigans. 

Salivary gland of Anopheles rossii. 

Salivary gland of Tabanus albimedius. 

Cells of the labial salivary gland of Hae- 
matopota. 

Scheme of the circulatory system ... 130 

The genital organs of Tabanus, male. 
The genital organs of Musca, male. 



XXIV 

Plate 



XXIX. 



XXX. 



XXXI. 



XXXII. 



XXXIII. 



XXXIV. 



XXXV. 



Fig. 


3. 


r ig. 


4 


t Ig. 


1 . 


Fig. 




Fig. 




Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


J. . 


Fig. 


n 


Fig. 


D. 


Fig. 


A 

^. 


Fig. 


1 

1 . 


Fig. 


o 

A. 


Fig. 


3 
J. 


Fig. 


A. 
T. 


Fig. 


C 

J. 


Fig. 


f. 
D. 


Fief. 


7. 


Fig. 


8. 


Fig. 


1 

X . 


Fig. 




■Tig. 


J. 


FisT. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


7. 


Fig. 


1. 


Fig. 


4. 


rig. 


J. 


Fig. 


4. 


r ig. 


c 

J. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


r ig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


7. 


Fig. 


8. 


Fig. 


9. 


Fig. 


10. 


Fig. 


1. 


Fig. 


2. 



list of illustrations 

Facing Page 

The genital organs of Culex, male. 

The genital organs of Hippobosca, male. 134 

Ovarian tube of Stomoxys. 

Ovarian tube of Culex. 

Common oviduct and connected structures 

of Musca. 
Spermatheca of Haematopota. 
Reproductive organs of Haemotopota, 

female. 

Spermatozoon from Musca nebulo ... 137 

Genital apparatus of Glossina palpalis. 
Genital apparatus of Musca bezzii 
Genital tract of Melophagus ovinus. 
Longitudinal section of ovaries, oviducts, 

receptaculum, of Melophagus ovinus ... 142 

Culicoides kiefferi, female. 

Head of larva of same. 

Claws and empodium of same. 

Last segment of larva of same. 

Larva of same. 

Pupa of same. 

Hind- and fore-leg of same. 

Antenna of Culicoides kiefferi, male ... 163 

Simulium striatum, female. 
Egg mass of same. 
Pupa of same. 
Larva of same. 
Egg of same, enlarged. 
Ventral view of head of larva of same. 
Dorsal view of same 



Egg of Phlebotomus papatasi. 
Phlebotomus papatasi, male. 
Larva of same. 

Phlebotomus papatasi, female. 

Pupa of same ... ... ... 

Larva of Anopheles rossii. 
Egg of Anopheles stephensi. 
Alimentary tract of larva of Culex con- 
color. 

Mental plate of larva of Anopheles rossii. 

Egg of Culex fatigans. 

Pupa of Anopheles rossii. 

Egg of Stegomyia sugens. 

Egg of Anopheles fuliginosus. 

Egg raft of Culex fatigans. 

Egg of Anopheles culicifacies ... 

Mandible of larva of Anopheles rossii. 
Upright forked scale. 



172 



181 



195 



LIST OF ILLUSTRATIONS 



XXV 



Plate 



Facing Page 



XXXVI. 
XXXVII. 
XXXVIII. 
XXXIX. 
XL. 

XLI. 
XLII. 



Fier. 


3. 


Upright forked scale. 




Fief. 


4. 


Maxilla of larva of Anopheles Tossii. 




Fief. 


5. 


Twisted upright scale. 




Fier. 


6. 


Broad wing scale. 




Fig. 


7. 


Inflated parti -coloured scale. 




Fig. 


8. 


Broad wing scale. 




Fig. 


9. 


Small spindle-shaped scale. 




Fig. 


10. 


Curved hair-like scale. 




Fig. 


11. 


Flat spindle-shaped scale. 




Fig. 


12. 


XT J 1 

Narrow curved scale. 




Fisr 


13. 


Flat abdominal scale. 




Fig. 


14. 


Spine from syphon tube of Ctdex larva. 




Fig. 


15. 


Syphon tube of larva of Stegomyia 








sugens. 




r ig. 


1 ft 

i D. 


oypnon ludc oi K^itiex jciiigGtis, 




Fig. 


17. 


Palmate hairs of larva of Anopheles rossii. 


198 


Fig. 


1 

1 . 


iitegotityici jcTSCtcitd, lemale. 




Fig. 


2. 


Citlex fatigans, female 


216 


Fig. 


1 

1 . 


/\7lOpn6lCS TUSSllj IClTlcllc. 




Fig. 


4. 


Anopheles ftil i^iitosttSj fcnicLle ,,, 


440 


Fig. 


1. 


Anopheles cuUcifactes, female. 




r ig. 


O 


J-i. f I UjJ f I b oii^jJni^fi'olf IcIlldlG 


4uv 


Fig. 


1, 


Anopheles costalis, female. 




Fig. 




j\nopneies junesms, lemaie .,, 




Fig. 


1. 


Tabanus speciosiis, male. 




Fig. 


2. 


Egg mass of same. 




Fig. 


3. 


Tabanus speciosiis, female 


289 


Fig. 


1. 


Haeniatopota plinnalis, female. 




Fig. 


2. 


Chrysops dispar, female ..." 


291 


Fief. 


1. 


Eggs of Tabanus bicallosus. 




Fig. 


2. 


Egg mass of same. 




Fig. 


3. 


Last abdominal segment of pupa of male 








of same. 




Fier. 


4. 


Last abdominal segment of pupa of female 








of same. 




Fief. 


5. 


Larva of Tabattus bicallosus. 




Fief. 


6. 


Pupa of same. 




Fig. 


7. 


Larva of Tabanus ditaeniatus. 




Fig. 


8. 


Pupa of same. 




Fig. 


9. 


Last abdominal segment of pupa of male 








of same. 




Fig. 


10. 


Egg of Tabanus ditaeniatus. 




Fig. 


11. 


Egg mass of same. 




Fig. 


12. 


Egg mass of Chrysops dispar. 




Fig. 


13. 


Larva of Tabanus virgo. 




Fig. 


14. 


Pupa of same. 





xxvi 



LIST OF ILLUSTRATIONS 



Plate Facing Page 





T^i o* 

r ig. 


1 


ornf m o cc r\x ca tvi 






Fig. 


16. 


Last abdominal segment of pupa of same. 


298 


XT TIT 




1, 


n/i H Ci^/T /I mii P Q^l f /7 T ATM 1 P 






Fig. 


2. 


Musca nebiilo, female 


334 


XT TV 


T^i cf 


1 

1 • 


^1 1 1 hf^aori 1 no" r*cx rr a 








2. 


T Jirfyp tr^iv fnr rparinp^ tahfim(i larvae. 






Fis' 


3. 


T fl Tftf^ HrfipH 1 n C pa CP 






T'"i0' 


4. 


AnnfVipr Qm^ill nfppnmo' pnp*p 






Fifif 

J- 'S- 


5. 


T^Vip mnr! pnrlnQnrp p"1?»qq i^irc; frnd lam 










hnttlpc; wifVi ciprpw tone? 


343 


XLV. 


Fig. 


1. 


Musca pattont, female. 






Fig. 


2. 


Musca bezzii, female 


349 


XLVI. 


Fig. 


1. 


Egg of Musca nebulo. 






Fig. 


2. 


Egg of Musca pattoni. 






Fig. 


3. 


Egg of Pliilaematomyia insignis. 






Fig. 


4. 


Egg of Stovioxys caJcitrans. 






Fig. 


5. 


Egg of Lyperosia exigua. 






Fig. 


6. 


Anterior spiracle of larva of Stomoxys 










calcitrans. 






Fig. 


7. 


Posterior spiracle of same. 






Fig. 


o 

O. 


Posterior spiracle of larva of Musca nebulo. 






r ig. 


Q 












myia insignis. 






Fig. 


10. 


Larva of Musca gibsoni. 






Fig. 


11. 


Puparium of Musca nebulo. 






Fig. 


12. 


Puparium of Glossina palpalis. 






Fig. 


13. 


Fupanum oi Htppooosca maculata 


■SCI 

351 


XLVII. 


Fig. 


1. 


Pliilaematomyia insignis, female. 






Fig. 


2. 


Philaematomyia gurnei, female 


356 


XT VTTT 


r ig. 


1_ 


1 1 lA'C'triill UUt'Ct' o I frill I dfC-^y I CllldlCi 






r ig. 


2. 


XjCH^l lUl ClryJlX iyClJl^ H i iJ'OtdllllS ^ 1 CllldlC > • • 


ooy 


"V T TV 


Fig. 


I. 


btomoxys calcitrans, lemale. 






r ig. 


2. 


L^yjJt^fUii lit' i^Xl^lvCiy IClIldiC ... •.. 


37'> 


T 

L,. 


Fig. 


1. 


Alimentary tract of larva oi labanus 










/T / ) .II'I /5 ^ ^ 1 i C 

illUltHUlltUh* 






Fig. 


2. 


Alimentary tract of larva of Stomoxys 










calcitrans. 






Fig. 


3. 


Mouth parts and pharynx of larva of 










Stomoxys calcitrans. 






Fig. 


4. 


Head of larva of Tabanus albimedius ... 


376 


LI. 


Fig. 


1. 


Glossina palpalis, male 






Fig. 


2. 


Glossina morsitans, female 


380 


LII. 


Fig. 


1. 


Hippobosca maculata, female. 






Fig. 


2. 


Melophagus ovinus, female 


409 


LIII. 


Fig. 


1. 


Ctenocephalus felis, male. 






Fig. 


2. 


Terminal segments of female of same. 





LIST OF ILLUSTRATIONS 



xxvii 



Plate Facing Page 



437 
437 





Pier 


3. 


Cllaw of cjatTip 




Fig. 


4. 

T. 


The ninth tergite of male of same. 




r ig. 


C. 

J * 


illlcll btyicL Ul Icllldie Ul bdlllC. 




r ig. 


D. 


J. lie antenud. oi bame ... ... 








Reference letters, Plates LIII to LVI 1 1 ... 


T TV 
JL<1 V . 


„. 
Jb Ig. 


1 

1 . 


rleacl OI h,chidiioph(x^a gcilliitcTccits. 




r Ig. 


O 
^> 


rTiiiu. cuAd Ul irivCt^x irriici/i'O, 




r ig. 


a 

J . 


UrnQ 01 manuDiium oi i^icrioc^^fiut'iis 












r ig. 


4 


iVld Allld Ul It^rtULi^j^rl'Ct'Cl'lo Ji^llo • 




r ig. 


J. 


JTLcdCl Ul 1 cllldlc \^ CfiilijLK^JJHClLU'O y C/tta. 




Fig. 


D. 


± lie lUbLi uiii Ul bdiiic. 




Fig. 


7. 


Distal end of mandible of same. 




Fig. 


8. 


Mandible of same. 




Fig. 


9. 


Distal end 01 labrum-epipnarynx or same. 




Fig. 


10. 


bense hair irom antenna 01 Leratophyllus 








fasciatus. 




Fig. 


1 1 

11. 


I he labrum-epipiiarynx 01 Ctenocephalus 








felts. 




tig- 


12. 


Antenna 01 Ceratophylliis fasciatus. 




Fig. 


13. 


T T 1 C t ill * r 1 

Head 01 Ltenoceplialus cams, lemale 


LV. 


Fig. 


1. 


Meso-and meta-thorax of Pitlex irritans. 




Fig. 


2. 


The same of Xenopsylla cheopis. 




Fig. 


3. 


1 he ninth tergite and sternite or same. 




Fig. 


4. 


The spermatheca or Ptilex irntatis. 




Fig. 


5. 


The same or Xenopsylla cheopis. 




Fig. 


6. 


The terminal abdominal segments of Ptilex 








irritans, male. 




FisT. 


7. 


The terminal abdominal segments of 








Xenopsylla cheopis, female 


LVI. 


Fig. 


1. 


Ceratophylliis fasciatus, lemale. 




Fig- 




T T 1 C J. L 1 J.1 1 . 1 

Head or Ctenophthalmus agyrtes. 




Fig. 


3. 


hciitdnophaga gallmaceus, remale. 




Fig. 


4. 


Dermatophyllus penetrans, female. 




Fig. 


5. 


Head of Lycopsylla novus. 




Fig. 


6. 


Xenopsylla cheopis, female 


T VTT 


r ig. 








Fig. 


/I. 


Terminal segments of same. 






■\ 

•J • 


Anal T^rnr'pcic; nf t^smp 




Fig- 


4. 


Pupa of same. 




Fig. 


5. 


Alimentary tract of larva of same. 




Fig. 


6. 


Salivary glands of the larva. 




Fig. 


7. 


Cells on the wall of the hind -gut of larva. 




Fig. 


8. 


Antenna of larva of same. 




Fig. 


9. 


Mandible of larva of Echidnophaga galli- 








naceus. 




Fig. 


10. 


Terminal segments of larva of same. 



440 



445 



450 



kxviii 



LIST OF ILLUSTRATIONS 



Plate 



Facing Page 



LVIII. 



LIX. 



LX. 



LXI. 



Fiar. 


11.1 


Fie. 


12. r 


Fie. 


3 f 

J. J.; 


Fie. 


14. 


Fig. 


15. 


Fie. 


16. 


Fig. 


1. 




2. 


Fig. 


3. 


r ig. 


4_ 


Fig. 


5. 


Fig. 


6. 


Fie. 


7. 


Fig. 


8. 


Fig. 


9. 


Fig. 


10. 


Fig. 


11. 


Fig. 


12. 


Fie. 


1. 


Fig. 


2. 


Fig. 


1. 


Fig. 


2. 


Fig. 


J. 


Fig. 


4. 


Fig. 


J. 


r ig. 


A 


Fig. 


7. 


Fig. 


1. 


Fig. 


2.) 


Fig. 


4.) 


Fig. 


3. 


Fig. 


5. 


Fig. 


6. 



LXII. Fig. 1. 



Fig. 
Fig. 
Fig. 

Fig. 



la. 
lb. 

0 



Circus method of controlling fleas. 



Antenna of larva of Echidiiophaga galli- 

naceus. 
Larva of same. 

Egg of Ctenocephaliis felis ... ... 439 

Nerve ganglia of Ctenocephaliis felis. 
Abdominal ganglia, highly magnified. 
Alimentary tract of Ctenocephaliis felis. 
Chitinous spines from proventriculus. 
Undeveloped ovarian tube. 
Reproductive organs of Ctenocephalus 

felis, male. 
Ovarian tube. 

Cross-section through proventriculus. 
Transverse section through upper end of 
proboscis. 

Transverse section through base of pro- 
boscis. 

Salivary glands of Ctenocephaliis felis. 

Distal portion of salivary duct ... 470 

Conorhiniis rubrofasciatiis, female. 
Cotiorhinus inegistiis, female ... 487 

Larva of Cimex rotundattis. 

Egg of Conorhiniis rubrofasciatiis. 

Larva of same. 

Second nymph of Cimex rotiindatus. 
Second nymph of Conorhiniis rubrofasci- 
atiis. 

Third nymph of Cimex rotiindatus. 
Third nymph of Conorhinus rubrofasci- 

atus ... ... 490 

Cimex rotiindatus, female, ventral aspect. 

Serrated hairs of Cimex. 

Cimex rotiindatus, male, dorsal view. 
Elytron of Cimex. 

Terminal segments of abdomen of Cimex 

rotiindatus, male ... ... 499 

Distal end of maxilla of Conorhinus rii- 

brofasciatus. 
Distal end of mandible of same. 
Maxilla of same. 

Distal end of mandible of Cimex rotiinda- 
tus. 

Cross-section through proboscis of Cimex 
rotundattis. 



LIST OF ILLUSTRATIONS 



xxix 



Plate 



LXIII. 



LXVI. 



LXVII. 



Fig. 


5. 


Fig. 


6. 


Fig. 


7. 


Fig. 


8. 


Fig. 


9. 


Fig. 


10. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


3. 


Fig. 


/. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


7. 


Fig. 


8. 


Fig. 


9. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


3. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


3. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 



Facing Page 
Cross-section through proboscis of Conor- 

hinus rubrofasciatiis. 
Terminal joints of leg of Cimex rotmidatus. 
Labium of Cimex rotiindatiis, from be- 
hind. 

Wing of Conorhinus rubrofasciatiis. 
Labrum of Cimex rotiuidatus. 
Proventriculus and salivary glands of 
Conorhinus rubrofasciatiis 

Cimex lectularius, male. 
Cimex lectularius, female. 
Egg of Cimex rotundatiis. 
Cimex rotundatiis, female, ventral view. 
Cimex rotundatiis, male. 
Cimex rotundatiis, female ... 



Alimentary tract of Cimex rotundatus. 
Tubular salivary gland of same. 
Branched salivary gland of same. 
Chitinous structures at end of head of 

Cimex rotundatus. 
Pharynx of Conorhinus rubrofasciatiis, 

from the side. 
Salivary pump of Conorhinus, dorsal 

aspect. 

Pharynx and salivary apparatus of Cimex 

rotundatus. 
Terminal filament of salivary valve of 

Cimex rotundatus, side view. 
The same, ventral aspect 

Reproductive organs of Cimex rotundatus, 
male. 

Accessory glands of same. 
Mass of sperms. 
Ovaries of Cimex rotundatus. 
Ovum of same. 

Section through Berlese's organ 

Phthirus pubis, female. 

Hind leg of Haematopinus tuberculatus. 

End of abdomen of Haematopinus vituli, 

ventral aspect. 
The same of Haematopinus tuberculatus, 
Pediculus capitis, female. 
End of abdomen of Pediculus vestimenti, 

male. 

Transverse section through the head of 
Pediculus vestimenti. 

Other transverse sections of same. 



501 



506 



514 



519 



529 



XXX 



LIST OF ILLUSTRATIONS 



Plate Facing Page 

Vertical longitudinal section through the 

head of same ... ... ... 538 

LXVIII. Fig. 1. Pedicinus etirygaster, female. 

Haematopinus tuberculatiis, female. 
Haematopiniis suis adventiciis, female. 
Haematopinus stephensi, female. 
Sternal plate of Haematopinus latus. 
The same of Haematopinus stephensi. 
The same of Haematopinus tuberculatus. 549 

LXIX. Fig. 1. Pediculus vestimenti, larva. 

Pedicuhis vestimenti, first nymph. 
Egg of same. 

Pediculus vestimenti, second nymph. 
Pediculus vestimenti, female ... ... 551 

LXX. Fig. 1. Anterior end of mid-gut of Pediculus ves- 
timenti. 
Cells near the oesophagus. 
Cells of the mid-gut in transverse section. 
Transverse section through the hind-gut. 
Transverse section through anterior lobes 
of mid-gut. 

Alimentary canal of same ... ... 556 

LXXI. Fig. 1. Reproductive organs of Pediculus vesti- 
menti, female. 
Proboscis of same. 

Chitinous framework of sucking apparatus 

of same. 
A cell of the fat body. 
Transverse section through the hind-gut 
of same. 

Edge of maxilla of Pediculus vestimenti. 
Reproductive organs of Pediculus vesti- 
menti, male ... ... ... 559 

LXXI I. Fig. 1. Hyalomma aegyptium, male, dorsal view. 

Amblyomma crenatum, male, dorsal view. 
Hyalomma aegyptium, male, ventral view. 
Ornithodorus savignyi, female, ventral view. 
Dorsal view of same. 

Aponomma gervaisi, female, dorsal view. 570 

LXXI II. Fig. 1. Capitulum of Ixodes angustus, female, 
dorsal view. 
Ventral view of same. 
Capitulum of Aponomma pattoni, female, 

ventral view. 
Capitulum of Hyalomma aegyptium, fe- 
male, dorsal view. 
Ventral view of same. 
Capitulum of Dermacentor andersoni, fe- 
male, ventral view. 



r ig. 


.J . 


r Ig. 


1 

I . 


Fig. 


9 


Fig. 


5. 


r ig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fie. 


7. 


rig. 


1 

1. 


rig- 


n 
^ , 


Fig. 


3. 


Fig. 


4. 


r ig. 


•J • 


Fig. 


1. 


Fig. 




Fig. 


3. 


Fig. 


4. 


t Ig. 


c 

J. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


rig- 


3. 


rig. 


A 

T-. 


rig. 


C 
J. 


r Ig. 


A 
u. 


Fig. 


7. 


■Tig- 


1 

1 . 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


/- 
o. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 



LIST OF ILLUSTRATIONS 



xxxi 



Plate 



Facing Page 



LXXIV. 



LXXV. 



LXXVI. 



LXXVII. 



LXXVIII. 



Fig. 


7. 


Fig. 


8. 


Fig. 


9. 


Fig. 


10. 


Fiar 


11. 


Fig. 


12. 


Fig. 


13. 


Fig. 


14. 


Fig. 


15. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


t ig. 


c 

J. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


r Ig. 


1 

1 . 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 



Capitulum of Margaropus annulatus, 

female, ventral view. 
Dorsal view of same. 

Capitulum of Rhipicephalus haemaphy- 
saloides, female, ventral view. 

Capitulum of Aiiiblyomma americanum, 
female, dorsal view. 

Capitulum of Haemaphysalis hispinosa, 
female, ventral view. 

Capitulum of Haemaphysalis leachi, fe- 
male, ventral view. 

Capitulum of Amblyomtua americanum, 
male, ventral view. 

Capitulum of Amblyomma testiidinarum, 
female, dorsal view. 

Ventral view of same ... ... 572 

Argas persicus, female, dorsal view. 
Ventral view of same. 
Argas reflexus, female, ventral view. 
Ornithodorus turicata, male, ventral view. 
Argas vespertilionis, male, ventral view. 
Ornithodorus mouhata, female, ventral 
view ... ... ... 581 

Larva of Argas persicus. 

First nymph of Ornithodorus savignyi. 

Larva of same. 

Stigmal plate of Dermacentor venustus. 
Stigmal plate of Dermacentor reticu- 

latus ... ... ... 587 

Ixodes ricinits, male, ventral view. 
Dorsal view of female of same. 
Ixodes aitgustus, male, dorsal view. 
Dorsal view of female of same. 
Eschatocephalus vespertilionis, male, ven- 
tral view. 

Cem^j:vo<^es i)M /MS, male, ventral view ... 594 

Rhipicephalus sanguineus, male, ventral 
view. 

Dorsal view of same. 

Rhipicephalus simus, male, ventral view. 
Dorsal view of same. 

Rhipicephalus appendiculatus, male, ven- 
tral view. 

Rhipicephalus haemaphysaloides, male, 

ventral view ... ... ... 602 

Margaropus lounsburyi, male, ventral 
view. 

Dorsal view of female of same. 



XXXI 1 



LIST OF ILLUSTRATIONS 



Plate 



Facing Page 



LXXIX. 



LXXX. 



LXXXI. 



LXXXII. 



LXXXI 1 1. 



LXXXIV. 



Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fief. 


5. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 




7 


Fiff. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 



Margaropus anniilatus decoloratus, male, 

ventral view. 
Dorsal view of female of same. 
Margaropus annulatus annulatus, male, 

ventral view. 
Dorsal view of female of same ... 607 

Autblyoinma cajennense, male, dorsal 
view. 

Dorsal view of female of same. 
Amblyomma hebraeuin, male, dorsal view. 
Dorsal view of female of same. 
Amblyomma variegatum, male, dorsal view. 
Dorsal view of female of same ... 619 

Aponomma pattoni, male, dorsal view. 
Dorsal view of female of same. 
Dermaceiitor andersoni, male, dorsal view. 
Dorsal view of female of same. 
Dermaceiitor albipictiis, male, dorsal view. 
Dorsal view of female of same ... 624 

Haemaphysalis concinna, male, ventral 
view. 

Dorsal view of female of same. 
Haemaphysalis leacJit, male, ventral view. 
Dorsal view of female of same. 
Haemaphysalis bispinosa, male, ventral 
view. 

Dorsal view of female of same ... 630 

Small iron cage. 

Calf box. 

Large iron cage. 

Goat dressed in cloth garment. 

Calf with belly bag. 

Cage for wild animals. 

Cage suitable for keeping snakes ... 642 

Superficial dissection of Argas persicus, 

female. 
Deep dissection of same. 
Triangular area showing the brain. 
Superficial dissection of Ornithodorus 

savignyi, female. 
Deep dissection of same ... ... 654 

Superficial dissection of Margaropus an- 
nitlatus, female. 

Deep dissection of same. 

Dissection of Argas persicus showing rela- 
tion of ovary, etc. 

Superficial dissection of Hyalomma aegyp- 
tium, female. 



LIST OF ILLUSTRATIONS 



XXXlll 



Plate 
LXXXV. 



Fig. 5. Deep dissection of same 



LXXXVI. 



LXXXVII. 



LXXXVI II. 



LXXXIX. 



Fig. 


5. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


7. 


Fig. 


o 

8. 


Fig. 


9. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


1. 


Fig. 


o 


Fig. 


3. 


Fig. 


4. 


Fig. 


5. 


Fig. 


6. 


Fig. 


7. 


Fig. 


8._ 


Fig. 


1. 


Fig. 


2. 


Fig. 


3. 


Fig. 


4, 


Fig. 


5. 



Facing Page 
... 657 



Longitudinal section through capitulum of 

Margaropus annulatus, female. 
Transverse section through the rostrum of 

Aponomnta gervaisi, female. 
A similar section further back. 
A similar section through basis capituli in 

front of porose areas. 
Transverse section through the posterior 

portion of basis capituli. 
Hypostome of Amblyomma testitdinarum, 

female. 

Hypostome of Ornithodorus savignyi, 
female. 

Mandible of Amblyomma testudinarttm, 
female. 

Mandible of Ornithodorus savignyi, female 660 

Transverse section through a diverticulum 

of Argas persicus. 
Transverse section through the salivary 

gland of the same. 
Male genital organs of Argas persicus. 
Salivary duct and lobules of Hyalomma 

aegyptiiim. 
Section through a diverticulum of Argas 

persicus. 

White gland of Argas ^ers/cws, male ... 673 

Laelaps sp ?., female, dorsal view. 
Tarsi and claws of first leg of same. 
Tarsi and claws of second leg of same. 
Leg of Pteroptics vespertilionis. 
Pteroptiis vespertilionis, female, ventral 

view ... ... ... 682 

Dissection of Porocephalus pattoni, male. 
Transverse section through the same. 
Porocephalus pattoni, male, ventral view. 
Mouth of same. 
Hook of same. 
Egg of same. 

Transverse section through salivary gland 
of same. 

Dissection of Porocephalus pattoni, fe- 
male ... ... ... 701 

Capitulum of Laelaps sp ?., female. 

Capitulum of male of same. 

Digit of mandible of same. 

Cyclops sp ?., female, ventral view. 

Lateral view of same ... ... 707 



ERRATA 



Page 38, for ' Chapter III', read 'Chapter IV'. 

Pages 43 and 347, for ' Homolomyia ', read ' Homalomyia '. 

Pages 162, 166, 319 and 409, for 'LATRIELLE', read ' LATREILLE." 

Page 183, for ' Neveau-Lemaire ' , read ' Neveu-Lemaire ' . 

Page 190, for 'Reamur', read 'Reaumur'. 

Page 192, for ' 4,300 feet ', read ' 1,600 ' ; for ' culcinae ', read ' culicine '. 

Pages 204, 245 and 252, for ' muritianus ' , re^^^^• ' mauritianus ' . 

Page 214, for ' Heteroncyha ', read ' Heteronycha '. 

Page 219, for ' Eratmapodites ', read ' Eretmopodites '. 

Page 248, for 'thelleri', read 'theileri'. 

Page 251, for ' pitcpfordi ', read ' pitchfordi ' . 

Page 255, for 'aibimanus', read ' albimanus ' . 

Page 268, for 'Chapter IV', read 'Chapter III'. 

Pages 273 and 293, for 'Sourcouf', read 'Surcouf'. 

Pages 274 and 294, for ' Gastrixodes ', read ' Gastroxides ' . 

Page 314, for ' Scrcophage ', read ' Sarcophaga ' . 

Page 326, for ' maceallria ' , read ' macellaria ' . 

Page 361, for 'Geoffrey', read 'Geoffroy'. 

Page 364, for ' Merlett ', read ' Marlatt '. 

Page 406, for ' Caetaerhina ' , read ' Crataerhina ' . 

Page 406, for ' Myiphthiria ', read ' Myiophthiria '. 

Page 407, for ' Ornithoctena ', read ' Ornithoctona ' ; for ' Sternopteryx ', read 

' Stenopteryx ' . 
Page 468, for 'Thompson', read 'Thomson', 
Page 512, omit the words ('see Appendix'). 



CHAPTER I 



INTRODUCTION 

Entomology as a branch of preventive medicine is a study of recent 
growth, dating only from the two discoveries which initiated the modern 
science of parasitology, viz., the demonstration by Manson of the role 
played by certain mosquitoes in the transmission of filaria, and of the 
mode of transmission of malaria by Ross. The latter discovery has 
proved of infinite value to the human race : the two, rapidly succeeding 
one another, placed the relations of the blood-sucking arthropods to 
the vertebrates on which they feed, in an entirely new light, and opened 
up a vista of possibilities undreamed of before. Insects which had 
previously been regarded as pests, detested on account of the immediate 
trouble and annoyance they cause, now became suspected as carriers 
of disease. 

Under the stimulus of Laveran's discovery of the parasite of malaria, 
and the proof of its causal relationship to the disease, the study of 
blood parasites was alread)' progressing rapidly. Once the way was 
pointed out, and the conception of a complex life cycle involving a 
change of host accepted, our knowledge increased by leaps and bounds ; 
every parasite present in the blood of a vertebrate was suspected of 
passing one phase of its existence in the body of an arthropod, and 
with each succeeding discovery there came a demand for further know- 
ledge concerning the life history, bionomics, and structure of the 
suspected carrier. Entomology has thus become a science accessory, 
in some of its branches, to protozoology, a knowledge of the insect and 
of the conditions governing its existence being an evident necessity for 
the proper study of the parasites which it harbours. 

It was soon recognized, however, that it is not only through their 
capacity to act as the intermediate hosts of protozoal parasites inimi- 
cal to man, that insects become of medical and economic importance. 
In many diseases, such as plague and cholera, while there is no sug- 
gestion that the insect is an essential factor in the continued existence 
of the causal organism, it is beyond doubt that it may be the means 



2 



MEDICAL ENTOMOLOGY 



of transmission from man to man, directly or indirectly. The r6le of 
house flies in the propagation of cholera, typhoid, and dysentery is now 
well established, and practical sanitarians take it into account in devising 
measures for their prevention and elimination. 

From the nature of the case, medical entomology is a specialized 
branch of the study of insects, dealing with them only in so far as they are 
concerned in the mode of infection in various diseases, or are in them- 
selves noxious. An expert knowledge of individual forms is required, 
rather than a general knowledge of the class. Moreover, the attention of 
the observer has to be directed on certain well-defined lines, which in 
many respects deviate from those on which the study of entomology is 
ordinarily carried out. The important facts to be ascertained are the rela- 
tion of insects to man and domestic animals, their food, method and 
time of feeding, and their life histories ; their relation to the disease in 
question, such as their distribution and its coincidence or otherwise with 
the area over which the disease occurs, and their seasonal prevalence ; 
their structure and physiology, with special reference to those internal 
organs which will constitute the environment of the parasite after it is 
ingested. Such matters as the relations of groups of insects to one 
another, their phylogeny, classification, etc., fall more properly within 
the domain of the systematic entomologist, who studies the class as a 
whole, as a branch of general zoology. At the same time some know- 
ledge of systematic work is a practical necessity, in order to be able to 
identify a suspected or incriminated species, and to follow intelligently 
the general literature on the subject. 

Although the medical and sanitary aspects of entomology are thus 
limited, it must be borne in mind that the study of any organism or group 
of organisms is materially aided by the study of allied forms, the analogy 
with which provides working hypotheses. Some acquaintance with the 
whole class, as regards their life histories, conditions of existence, struc- 
ture, etc., is therefore essential, as a foundation on which to build up an 
expert knowledge of the groups of practical importance. Familiarity 
with what occurs in non-disease carrying forms has led on many occasions 
to the disclosure of important facts regarding true carriers. Special 
attention in this connection is due to those arthropods which harbour 
' natural' non-pathogenic parasites, for both the parasite and its host are 
in many cases closely related to others which are concerned in the etiology 
of disease. The student will do well to remember that Ross's work on 
proteosoma in sparrows preceded his demonstration of the life cycle of 
the parasite of human malaria. 



THE PHYLUM ARTHROPODA 



3 



The foregoing paragraphs will explain the point of view from which 
this book has been written, and the arrangement of the succeeding chap- 
ters. The second chapter is devoted to the anatomy of the Diptera, 
the subject being dealt with at some length, in order that it may serve as 
an introduction to the anatomy of the other groups of arthropods. The 
first section, dealing with the external anatomy, includes also an account 
of those characters on which the accepted systems of classification are 
built. In the following chapters each group of arthropods which is 
concerned with the transmission of disease is dealt with separately, as 
regards classification, anatomy, and technique, etc., a list of the principal 
papers dealing with the group being given at the end of the chapter. For 
further references the lists given at the end of these papers should be 
consulted. 

Some knowledge on the part of the reader of the diverse modes in 
which the arthropods may affect man and the domestic animals may be 
safely assumed, and it will not be necessary to enter into a general discus- 
sion of such matters here ; the economic importance of the various groups 
will be discussed as occasion arises, so far as it falls within the scope of a 
book of this nature. There are, however, certain points regarding the 
zoological position of the blood-sucking forms which call for a brief 
mention. 

The phylum arthropoda is one of the principal divisions into 
which the metazoa, or many celled animals, are divided. It is an 
extremely large one, and contains an enormous variety 
of forms. According to Shipley, at least seven -eighths Zoo'og'cal position 
c 4.U 4^ 1 r f ^v, ij of the blood-sucking 

oi the protoplasm on the suriace or the world is Arthropoda 

contained within the skins of arthropods, while in 

size and outward form they vary from the lobster to the most minute 

midge. 

Briefly, the essential characters of the phylum are metameric segmen- 
tation, the presence of jointed appendages, typically one pair to each 
segment, and a more or less hard exo-skeleton ; the heart is dorsal in 
position, and the nervous system ventral, except in the head, where a 
part of the brain is dorsal ; the body cavity is a haematocoele. The 
phylum is divided into five classes, as follows : — 

Crustacea : Crabs and lobsters, shrimps, cyclops. 

Protracheata : Peripetus. 

Myriapoda : Centipedes and millipedes. 

Insecta : Insects. (Sometimes called hexapods). 

Arachnida : Spiders, ticks, mites. 



4 



MEDICAL ENTOMOLOGY 



It is only in the last two classes that blood-sucking forms occur. The 
INSECTA are distinguished by the following special characters. The body 
is divided into three well-marked regions, the head, thorax, and abdomen. 
The head bears one pair of antennae, and three pairs of variously modi- 
fied mouth appendages. There are three pairs of legs in the adult, and 
generally two pairs of wings. The abdomen bears no appendages as a 
rule. Metamorphosis is usually complete, the young differing markedly 
from the adults. 

The class is divided into a number of orders, in only four of which are 
there blood-sucking forms. These are as follows : — 

DiPTERA : Flies. These are distinguished at once by 

having only one pair of wings, 
the metathoracic pair being re- 
presented by the halteres. The 
larva is a maggot-like creature, 
distinguished from the beetle 
larva by the absence of legs. 

SiPHONAPTERA : Fleas. These are wingless insects, with 

the body laterally compressed. 
Metamorphosis is complete, the 
early stages resembling those of 
the Diptera. All are blood- 
sucking and parasitic. 

RHYNCHOTAor Hemiptera: Bugs. Characterized by a jointed sucto- 
rial proboscis, which can be folded 
under the head. The prothorax 
is distinct from the other seg- 
ments, and the body compressed 
in the dorso-ventral direction in 
those forms which are parasitic. 
Many feed on vegetable juices. 
Anoplura : Lice. Small wingless insects, with a soft 

integument. The thorax is 
indistinctly segmented, and 
the body compressed in the 
dorso-ventral direction. All are 
parasitic. 

The ARACHNIDA are distinguished by having the head and thorax fused 
into one mass, the cephalothorax ; the remainder of the body does not 
usually consist of distinct segments. There are no antennae. The first 



THE ORDER ACARINA 



5 



pair of appendages, corresponding to the mandibles of insects, are called 
the chelicerae, the second the pedipalps ; when the second pair has a jaw- 
like portion, the two may be fused with the second maxillae to form the 
labio-maxillary dart or hypostome. There are four pairs of legs in the 
adult. The alimentary canal is straight, and the anus ventral, not termi- 
nal. Metamorphosis is incomplete, the young generally resembling their 
parents. 

The blood-sucking forms are confined to one order, the acarina, in 
which the body is soft rather than rigid, is non-articulated, and usually 
either rounded or oval. The thorax and abdomen are fused together 
as a rule, though the}^ may be separated by a groove, the anterior 
portion being spoken of as the capitiihiin. The mouth parts are adapted 
for the purpose of attaching the animal to its host while sucking. Re- 
spiration is carried on by tracheae, the position of the stigmata or respi- 
ratory openings being important in classification. Metamorphosis is 
incomplete, the larva resembling the parent, but possessing only three 
pairs of legs, while the nymph and adult have four. The order is 
divided by Ray Lankester into seven suborders, only four of which 
concern us. 

Suborder Metastigmata. Acarina in which the integument 

is mostly hard ; a pair of stig- 
mata is situated above and be- 
hind the base of the fourth legs. 
This suborder contains the 
Gamasidae, and the Ixodidae. 
It is to these two families that 
the blood-sucking acari, ticks, 
and mites belong. (Chapters 
viii and ix.) 

Suborder Prostigmata. Acarina in which the stigmata 

when present lie close to, or 
above the base of the chelicerae; 
they are absent in some of the 
aquatic forms. The integu- 
ment is soft, but with sclerites; 
those on the ventral surface 
apparently represent the proxi- 
mal segments of the legs em- 
bedded in the body. This sub- 
order contains the families 



6 



MEDICAL ENTOMOLOGY 



Suborder. ASTIGMATA. 



Suborder. Vermiformia. 



Arachnida insertis sedis. 



Tromhid iidae, Hydrach n idae, 
Holacaridae, and the Bdellidae. 

Degenerate acari with soft skins 
and no tracheae ; they are par- 
asitic and approach the Pro- 
STlGMATAin the development of 
the integumental sclerites. This 
order contains the Sarcoptidae. 

Degenerate acari without tracheae 
and eyes ; the posterior portion 
of the body is protruded into an 
annulated tail ; the four pairs 
of legs are short, and three- 
jointed. This order contains 
the Demodicidae. 

Pentastomida show many dis- 
tinct arthropod characters ; they 
will be dealt with in Chapter x, 
Section \. 



It will be noticed that the blood-sucking forms are distributed some- 
what irregularly throughout the arthropoda, and are not confined to any 
one order, though some orders, such as the Siphonaptera, are exclusively 
blood-sucking and parasitic. The habit is in itself no indication of 
relationship, as is shown by the fact that it may be present in the female 
and absent in the male. Mouth parts which have become adapted for 
the purpose of piercing the skin and sucking up fluid nourishment are, in 
fact, formed from the same elements as those which are adapted for the 
ingestion of solid food, or fluid obtained from other sources. The mouth 
appendages, that is, the mandibles and first and second maxillae, are of 
such a type that they can, without any very great divergence from their 
ancestral form, be adapted to serve such a purpose. The form of ap- 
paratus which has evolved in the different families necessarily shows a 
good deal of variety, but it can usually be resolved into portions corre- 
sponding with the mouth appendages of non-blood-sucking forms. In the 
ticks, for instance, the mandibles or chelicerae make the wound, while 
the sucking tube up which blood is drawn is formed by their apposi- 
tion to the hypostome. In the bugs the mandibles and maxillae 
are of great length, the former being so apposed as to form a 
channel with a circular lumen, while the maxillae are armed with cutting 



ZOOGEOGRAPHICAL REGIONS 



7 



Geographical 
Distribution 



teeth and are used to pierce the skin. In the Diptera the piercing 
appendages may be the mandibles and first maxillae, or the second maxillae, 
while the sucking tube is formed by the outgrowth from the pharynx of 
two spatulate slips, one dorsal and the other ventral. . Secondary modifi- 
cations, such as flattening of the body, leathery consistence of the skin, 
etc., are developments consequent on the adoption of a parasitic habit. 

For the purpose of defining the distribution of animals, the surface of 
the earth is divided by zoologists into certain areas. 
According to Wallace, Sclater, and others, there are six 
regions, as follows : — 

Europe, the temperate parts of Asia, and the 
north of Africa ; Iceland and the islands in the 
Atlantic. It is limited by the Himalayas and 
the Indus. 

Africa, including its islands, except the north ; 
Arabia. 

India and the neighbouring islands, Cej'lon, 
Java, Borneo, etc. ; it includes also the 
Philippines. 

The Continent of Australia, New Zealand, the 

Celebes, and the neighbouring islands. 
America north of Mexico, and Greenland. 
Mexico, the West Indies, Central and South 
America. 



Palaearctic : 

Ethiopian : 
Oriental, or Indian 

Australian : 

Neartic : 
Neotropical : 



CHAPTER II 



SECTION I 

ANATOMY AND PHYSIOLOGY OF THE BLOOD-SUCKING 

DIPTERA 

The anatomy and physiolog}' of the blood-sucking arthropods concern 
the parasitologist in two ways. In the first place, some acquaintance 
with the external characters by means of which the various forms are 
separated from one another is essential, in order that the systematic posi- 
tion of the particular species with which one is concerned may be 
determined ; the published descriptions of species are written in highly 
technical language, and without some general knowledge of the structures 
to which the terms are applied it would be impossible to follow them. 
Secondly, a good working knowledge of the internal anatomy is indispen- 
sable in the study of the parasites of insects. Without such knowledge 
the relations of the parasite to its host, and its possible wanderings in the 
body of the host, cannot be properly understood. Moreover, unless one 
knows the relations of the internal structures to one another and to the 
exo-skeleton, one cannot arrive at a satisfactory method of performing 
routine dissections. 

In this chapter it is proposed to deal with the Diptera from the points 
of view suggested above, describing the structure and indicating as far as 
possible the function of the parts. In doing so the general principles of 
the anatomy and physiology will be explained as occasion arises, in order 
that, these having once been dealt with, they need not be further referred 
to in connection with the other blood-sucking insects. The structure of 
these will be considered under their separate chapters, as they differ too 
much in their general arrangements to be conveniently considered to- 
gether with the Diptera. The examples dealt with will be almost entirely 
blood-sucking flies, and the statements made are not necessarily 
generalizations for the whole order, unless this is stated or implied. 

As regards textbooks on insect anatomy and physiology, Packard's 
will be found most useful, though it is now out of date. Berlese's large 



GENERAL STRUCTURE 



9 



and fully illustrated work is very valuable for reference, and contains an 
extensive bibliography. Most of the larger w^orks on zoology contain a 
certain amount of general information on the subject, dealt with mainly 
from the comparative point of view. To those who have no previous 
acquaintance with structural entomology Miall and Denny's account of 
the cockroach is strongly recommended ; the authors have used their 
type to set forth in a masterly fashion the main points in the anatomy 
and physiology of insects, and there could be no better preparation for 
work with insects than the study of this admirable little book. 

A list of papers dealing with particular forms is given at the end of 
this chapter, and the worker may consult these as occasion arises. For 
further references, especially to the older and less accessible literature, 
the bibliography in Berlese's book, or the lists given in the special papers, 
may be consulted. Most of the papers of practical value are compara- 
tively recent, and are to be found in the larger libraries, 

GENERAL STRUCTURE 

Insects present the characteristic features of the phylum arthropoda, 
that is to say, they have a more or less elongated body, with a mouth 
at one end and an anus at the other, a central nervous system concen- 
trated in the head, and a ventral chain of ganglia; the body is metameri- 
cally segmented, and each segment bears typically a pair of jointed 
appendages ; the body cavity is not a true ccelom, but a haematocoele, in 
communication with the dorsal blood vessel. The class insecta is 
specially distinguished by the separation of the body into three well- 
defined regions, the head, thorax, and abdomen ; only three pairs of 
legs are present, and there are usually two pairs of wings. The order 
diptera is separated from other insects chiefly by the transformation 
of the hind pair of wings into the structures known as halteres or 
balancers, and by the adaptation of the mouth parts to form a sucking 
organ. 

By metameric segmentation is meant, that the body of the animal is 
made up of a number of separate segments or metameres, arranged one 
behind the other in the long axis of the body. (Plate I, fig. 3.) In insects 
there are said to be typically about twenty segments, of which the first 
six go to form the head, the next three to the thorax, and the remainder 
to the abdomen. Each segment should bear a pair of appendages, but 
in the adult insect only those on the head and thorax remain, and those 
on the head are always very highly modified. It is possible that certain 



10 



MEDICAL ENTOMOLOGY 



parts of the external genital organs are the representatives of true 
abdominal appendages. At a very early stage in the evolution of insects 
each metamere is believed to have been a replica of its neighbour, and 
this condition of affairs is found to a certain extent in the early stages of 
the present forms ; but in the adult the primitive arrangement of the seg- 
ments is obscured, and can only be recognized in certain parts of the 
animal. The most obvious segmental markings are to be found in the 
exo-skeleton, and particularly in the abdomen, and the term ' segment ' 
has come to be used with a special meaning in this connection. In the 
head there is little trace of the original arrangement to be found, and 
the extent of the various segments is a debatable matter. In the thorax 
each segment bears a pair of legs, but on account of secondary changes 
brought about by the growth of the wings the segments have developed 
unequally. In the internal anatomy the only organs which show traces 
of a segmental arrangement are the tracheae or breathing tubes, of which 
there are as a rule one pair to each segment, and the ventral chain of 
nerve ganglia. 

The Diptera are the most highly specialized as well as one of the most 
numerous orders of the class, and in them we find that the fusion of the 
segments has gone further than in other orders. As a result of the great 
development of one pair of wings, with the muscles which act upon 
them, the middle segment of the thorax has become greatly increased in 
extent at the expense of the others. In the abdomen there is, through- 
out the order from the simple forms upwards, a general tendency to a 
reduction in the number of the visible segments, and a corresponding 
concentration of the internal structures. This is frequently accompanied 
by a transformation of the exo-skeleton of the terminal segments into 
organs connected with the function of reproduction. 

Insects, like other arthropods, possess a more or less rigid integument, 
which encloses and protects the soft parts, and at the same time pro- 
vides attachments for the muscles of the body, all of 

The exo-skeleton ^yhich have their origins and insertions on the internal 
and its appendages 

surface of the exo-skeleton. The appendages consist 
of outgrowths of the integument, containing muscles, nerves, and other 
structures, and the joints in them are formed by a moulding of the outer 
layer. There is no true internal skeleton, but the exo-skeleton sends in- 
wards certain processes, often termed the endo-skeleton ; these occur in 
situations where either greater structural stability or additional surface 
for muscle attachment is required. 

The nature of this integument is of considerable importance from 




11 



PLATE I 



Figure 1. Head of a Muscid fly, seen from the front, with the 
proboscis removed, pt.s., the ptilinal stiture. f., 
frons. Oct., the ocellar tubercle (shown enlarged in 
figure 4). 

Figure 2. The same, seen from behind. 

Figure 3. Diagram showing the segmentation of a primitive 
insect, after Berlese. The segments are numbered in 
order. Six are shown in the head, five only being 
represented in most insects. The last three head 
segments have appendages, which become a part of 
the proboscis in the Diptera. The course of the 
alimentary tract is indicated, s., stoniadaeum. ms., 
mesenteron. p., proctodaeum (page lOl). 

Figure 4. The ocellar triangle of Mnsca, showing the three 
pigmented ocelli and the ocellar bristles. 

Figure 5. A section through chitin, to show the chitinogenous 
cells and the laminae, h., a hair, in direct connection 
with a chitinogenous cell. From Miall and Denny. 

Figure 6. Head of male Tahanus seen from the front. An 
example of a holoptic fly. Compare Plate III, 
figure 3. 



THE EXO-SKELEtON 



ll 



the point of view of technique. Rather less than half its total weight 
consists of the substance known as chitin, the peculiarly resistant 
properties of which are a formidable obstacle in the manipulation of 
insect tissues. Chitin is insoluble in acids and alkalis, in alcohol and 
ether, and in fact in all the ordinary laboratory reagents. It is also 
extremely impermeable, and unless apertures in the integument are made 
reagents will not penetrate to the soft tissues. It is pigmented, and when 
free from cellular material is more or less transparent. Its colour can 
be readily removed by bleaching agents, such as chlorine gas. At the 
moment of emergence from the pupal covering the chitin of the imago is 
soft and colourless, and it is only after exposure to air and light that 
it becomes pigmented and rigid. When in thin layers, with much cellu- 
lar material, it forms a tough membrane, but when in thick sheets it has 
only a small amount of resilience. It resists the action of heat, but 
is made harder and more brittle by even such moderate temperatures as 
are used in a paraffin bath. Prolonged immersion in alcohol has the 
same effect. 

The disposition of the chitin in the integument is as follows. (Plate 
I, fig. 5.) On the internal surface of the exo-skeleton there is a 
single layer of cells set on a thin basement membrane. These are the 
chitinogenous cells, and external to them there are found many layers of 
solid and structureless chitin, which has been secreted by the cells 
in very much the same manner as that in which the nails of vertebrates 
are produced. The basement membrane and the chitinogenous cells 
form a continuous layer throughout the body of the insect, and there 
is always a layer of chitinous tissue external to them, the thickness 
of which is varied in accordance with the structural requirements. 
In such parts as the thorax, where strength is necessary on account 
of the great development of the wing muscles, the layer of chitin is 
very thick, while in the region of joints, where flexibility is required, 
it is thin. But it is important to remember that even in thin sheets 
chitin is quite impermeable to any of the ordinary fixatives. 

The hairs and scales which are present on the integument, and which 
are so much used in classification, are outgrowths from the exo-skeleton. 
They are of two kinds, sensory hairs and others the function of which is 
unknown. The sensory hairs, such as those found at the distal end of 
the proboscis, on the palps, and on the antennae in some forms, are 
hollow, and contain delicate filaments of nervous tissue, enclosed in a 
central canal. They arise from single cells of the chitinogenous layer, 
the base of each hair piercing the chitinous laminae, and emerging from 



i2 MEDICAL ENTOMOLOGY 

the integument at a small pit. At the base there is a small bipolar gang- 
lion cell. 

In the Muscoidean flies the integument is adorned with many large 
bristles, called macrochaetae. These are arranged in a definite man- 
ner, providing most useful characters in classification. Since their 
value was pointed out by Osten Sacken great attention has been paid to 
them by dipterologists. A discussion of chaetotaxy, as this branch of 
descriptive entomology is termed, will be deferred until the regions on 
which they occur have been described. 

Osten Sacken has some interesting remarks on the possible function of 
these large bristles. It had been previously suggested by Macquart that 
their purpose was to protect the fly from collisions, such as its rapid flight 
might render it liable to, and the ingenious author carries this suggestion 
a little further. He points out that macrochaetae occur almost solely in 
those flies which are pedestrian in habit, using their legs in the search 
for food, in attacking other insects, and in oviposition, while in those 
flies which are mainly aerial in habit, and use their legs only for alighting, 
large bristles are rare. In Tabanus, for instance, which merely uses its 
legs so far as is necessary in finding a suitable place to make a wound in 
the skin of the host, the bristles are insignificant, while in the domestic 
house flies, which run about over the food surface, and search place 
after place, the bristles are well developed. In the Tachinidae, which 
parasitise caterpillars, many large macrochaetae are always present. 
It is evident that flies of an aerial habit, which spend their lives mainly 
either at rest or on the wing, and which have moreover the faculty of 
poising or hovering, will be much less liable to sudden collisions than 
those which have a pedestrian habit. He concludes that the macroch- 
aetae are organs of orientation, fulfilling much the same function as the 
whiskers of a cat. 

The exo-skeleton is not of uniform thickness throughout, but is 
divided up into numerous plates, each of which has received a distinct- 
ive name ; these are often separated from one another 

The nomenclature i i • , i j- • • • i 

. , , ^ by membraneous mtervals. The divisions are mainly 

of the exo-skeleton / . 

in the transverse direction, and represent typically the 
lines of separation of the metameres ; in the Diptera, they are, of 
course, greatly modified from the primitive condition, and it is often a 
matter of some difficulty to decide which of the primitive plates a parti- 
cular portion of the integument may represent. The subject is of 
academic rather than of practical importance, and it will suffice if it is 
touched on it only so far as to explain the terms in use. 



THE HEAD 



13 



Audoin supposed that the exo-skeleton of a primitive segment was 
composed of eight chitinous plates, arranged in pairs, two dorsal, two 
ventral, and two lateral plates on each side. Although this is not 
generally accepted as a type to which the very numerous and diverse 
forms may all be referred, his nomenclature has been preserved, with 
some modifications. He termed the dorsal plates the terga, the ventral 
the sterna, the pair of lateral plates contiguous with the terga the 
epimera, and the pair contiguous with the sterna the episterna. The 
two lateral plates when fused together are known as the pleura. Such 
a primitive arrangement is not to be looked for in the Diptera, and it 
is best to regard the terms as descriptive only, without laying too 
much stress on their significance, especially since hardly any two authori- 
ties are agreed on the point. In the head the various segments have 
become fused together to form a chitinous box, often termed the head 
capsule, and few if any really reliable indications of the original segmenta- 
tion are to be found in the adult insect. In the thorax a nearer approach 
to the type is found, but on account of the development of extra plates, 
and the displacement of others, it is very difficult to refer them to 
the type, especially in the case of the lateral plates. In the abdomen the 
arrangement is simple, as the terga and the sterna are preserved, and the 
interval between them occupied by a soft membrane, which, as it 
represents the pleural plates and bears the openings of the breathing 
tubes, is termed the pleural membrane. 

Each chitinous plate is separated from its neighbour by a narrow 
interval which is filled in either by soft membrane or by thinner chitin, 
and in this way the whole body of the insect is provided with a series of 
joints, which enable the various segments to move on one another. The 
head is united to the thorax by a flexible neck ; the segments which make 
up the thorax are firmly welded together for the most part, but there is 
a membraneous interval in the lateral wall which permits of a certain 
amount of expansion ; in the abdomen each dorsal and each ventral plate 
is connected with those in front of and behind it by means of a narrow 
strip of membrane. The dorsal plates are connected with the ventral 
ones by the pleural membrane. 

THE HEAD— (Plates I and III) 

The head capsule is a rounded and compact box, composed of the chiti- 
nous plates which belong to the exo-skeleton of the first five* segments 

* Of the six segments which should go to make up the head, the third is absent in the 
majority of insects. 



14 



MEDICAL ENTOMOLOGY 



of the body. The appendages of these segments are all highly modi- 
fied for special functions, the first two in connection with the special 
senses, the remaining three in connection with the mouth. The head 
in the Diptera is relatively large, but this is not due entirely to the 
development of the brain, but to the presence in the head of certain 
large air sacs which have an important function in connection with the 
sucking apparatus. In addition to the brain and the air sacs, the head 
contains the pharynx or sucking pump, and the muscles of the head ap- 
pendages. The shape varies from that of a flattened dome, as in the 
Tabanidae, to a more or less regular sphere, as in the Muscidae. The 
antero-superior surface is rounded, and bears the antennae at its most 
anterior point. The posterior surface is usually flattened, and may be 
concave. Its lower portion is occupied by the base of the proboscis, 
while about its middle there is the occipital foramen, to the boundaries 
of which the membrane of the neck is attached. The foramen is usually 
supported by a horseshoe-shaped arch. 

The various parts of the head have received special names for descrip- 
tive purposes. Unfortunately a good deal of confusion exists in the 
nomenclature of this region, for many of the terms are merely distinctive 
names employed in systematic work, and can only be properly applied to 
particular groups of flies, while others have originated in attempts to 
determine the homology of the head. 

In the Orthorraphic flies the angle at which the posterior and superior 

surfaces join one another is termed the occiput. The area in front of 

this, which may be conspicuous, as in the Culicinae, 
Regions of the head . ' , , t r r , • 

is known as the vertex. In front of this, and between 

the eyes, is the frons. The eyes occupy the entire lateral regions of the 
head ; when they are separated from one another by a definite space the 
fly is said to be dichoptic, while if there is only a very narrow interval 
the fly is said to be holoptic. The antennae arise at the anterior end of 
the frons, and may have at their bases a raised plate, as in the Tabanidae, 
in which it is known as the callus. Below the antennae there is a 
median plate, generally produced forwards, and forming the distal limit of 
the anterior surface ; this is known as the clypeus or face. The region 
below the eyes and external to the clypeus on each side is the gena, or 
cheek. The median posterior area extending from the base of the pro- 
boscis towards the occipital foramen is termed the gular region. It is 
generally membraneous in the Orthorrapha. 

In the Muscoidean flies, among which are the blood-sucking Muscidae, 
the shape of the head is rather rounder than in the Orthorrapha, and the 



THE MUSCID HEAD 



15 



structure of the wall is modified. The most striking and indeed the 
characteristic feature of the head in this group is the presence on the 
front of a long arched suture, commencing transversely above the 
antennae and extending downwards on each side of them, almost to the 
distal border. This is the ptilinal suture, and marks the place at which 
the ptilinal sac was pushed out at the time of the emergence of the 
imago from the puparium. The shape of the head is further modified 
by the increase in size of the basal joints of the antennae, which are pen- 
dulous, and rest in hollows on the anterior surface. The base of the head 
is also altered by the fact that a part of the wall has become merged with 
the proboscis, as will be explained shortly, and has become retractile. 
When the head is viewed from behind the whole of the posterior wall is 
seen to be chitinous, while at the lower border there is a rounded foramen 
between the anterior and posterior surfaces, through which the proboscis 
is protruded. The gular region has, therefore, become merged into the 
posterior wall of the first part of the proboscis. The aperture through 
which the latter is pushed out is sometimes referred to as the buccal 
orifice, a most unfortunate term, for it is some distance posterior to the 
structure universally known as the pharynx, and has nothing whatever to 
do with the mouth parts. It is better to use the term epistomal orifice, 
as the thin plate of chitin in front of it is known as the epistoma. 

The terms used in describing the Muscid head (Plate HI, fig. 1) are 
somewhat perplexing, mainly on account of their multiplicity. The area 
enclosed by the lateral arms of the ptilinal suture is known as the 
ptilinal area, the facial depression, or the front. It is almost entirely 
made up by the clypeus, for which alternative names are the face, facial 
plate, mesofacial plate. The antennae may lie in deep or shallow 
grooves, termed the fossae of the facial plate, or the antennal grooves. 
The grooves may be separated by a ridge, termed the facial carina, and 
this may be produced forwards in its lower portion. The lateral margins 
of the ptilinal area may be thickened into ridges, termed the facialia, 
or the facial ridges, or vibrissal ridges. They terminate in pro- 
minent angles known as the vibrissal angles. Below the facial 
plate or clypeus there is a small mesial plate, forming the boundary of 
the epistomal orifice, and termed the epistoma. The orifice itself, 
through which the upper part of the proboscis passes out in extension, 
is also known as the oral orifice or buccal orifice, and an oral cavity 
is mentioned, supposed to be bounded in front by the epistoma. 
Below the epistoma on the anterior surface there is a transverse plate 
regarded by many authors as the clypeus, the upper and larger plate 



16 



MEDICAL ENTOMOLOGY 



referred to above being considered as derived from other parts of the 
head. This plate corresponds to the anterior arch of the fulcrum, and 
will be described in more detail further on. At the upper end of the 
ptilinal area there may be two small plates, the lower one of which sup- 
ports the antennae; the upper one is termed the hiniile. 

The- area behind the ptilinal suture is divided into three lateral por- 
tions, the extent of which will be seen from the figure. The frontalia 
are also known as the frontals, or the mesofrontals, the parafrontals as 
the geno-vertical plates, and the parafacials as the sides of the face, or 
the genae. The term cheek is applied to that portion which has already 
been described as the gena. 

Most of the above terms are taken from Townsend's paper on the 
taxonomy of the Muscoidean flies, to which the reader who wishes to 
study systematic dipterology will do well to refer. The difificulty in 
following descriptions is not so great as the multiplicity of terms in use 
would suggest, for most papers are illustrated with diagrams, and the 
meaning of the words can be ascertained by a reference to the figures. 

The eyes in the Diptera do not differ materially from those in other 
insects, descriptions of which are to be found in most text-books on 
Th E es -Zoology. The external surface is made up of a large 

number of facets, usually equal in size and shape, and 
generally hexagonal, with rounded corners. (Plate III, fig. 2.) They 
may be pilose, i.e., covered with short hairs, or naked, the latter being the 
usual condition. They are of various colours, and the colouration may 
be of importance in the determination of the species ; this is especially 
the case in the Tabanidae, in which the eyes are most beautiful objects. 
Unfortunately the colour fades rapidly on the death of the fly, and both 
it and the markings should be noted in fresh specimens. 

In addition to the compound eyes there may be two or three ocelli, 
situated on the vertex of the head, generally in a small raised triangle. 
(Plate I, fig. 4.) In the fresh state they are seen as small spots of 
pigment ; in cleared preparations the pigment is readily dissolved out, 
and the situation of the ocelli shown by the clear spaces which remain. 

The antennae (Plate II.) are sense organs, which probably have for 

their function the perception of sounds and air currents. They are well 

. . supplied with nervous tissue and air tubes, and have 

The Antennae ^ • , • , • , , 

peculiar sense pits , m which the olfactory sense 

is believed to be located. They are, as previously stated, the 
appendages of the second segment of the head, and in all cases they 
retain the original form, that is to say, they are composed of a 



PLATE. tt 




Fig. 2. 



if 

K 

:i';f 



1 li 

/ 




Fig. 3 




Fig. 5. 



Fig. 6. 



Fig. 




Fig. 7. 



17 



PLATE 11 



Types of Antennae 

Figure 1. Miisca iiebiilo. x 54 

Figure i. Glossiiia suhtiiorsitans. X 60 

Figure 3. Hippobosca inaculata ; the sliort cubical antenna, 
consisting of only one joint, is shown in its pit. x 95 

Figure 4. Ciilex fatigans, <? X 54 

Figure 5. Clirysops dispar. X 36 

Figure 6. Lyperosia mimita. x 110 

Figure 7. Tahanits albiineditis. X 42 



THE ANTENNAE 



17 



number of joints, set one behind the other. Their appearance differs 
greatly in the different genera of Diptera, but in general there are 
two forms, one met with in the Orthorrapha and the other in the 
Cyclorrapha. The distinction between the two forms was used by 
the older systematists to divide the Diptera into the two primary divi- 
sions known as the Nematocera and the Brachycera, which correspond 
roughly with the two divisions named above (see Chapter III), In the 
Nematocera all the joints of the antenna are similar to one another, 
except one or two at the base, which are usually larger. There may be 
from four to sixteen joints, each cylindrical or sub-cylindrical in shape, 
and generally tapering a little from base to apex. The joints may be 
adorned in various ways, and the adornment may differ in the two sexes, 
thus offering a ready means of distinguishing them. They may be plu- 
mose in both sexes, as in Phlebotomus, or plumose in the male and not in 
the female, as in Ciilex. The whorls of hairs are attached to the base of 
each segment. In the Brachycerous flies the antenna consists of a small 
number of dissimilar joints, of which the basal ones are the most modified. 
In the Tabanidae, which are Brachycerous Orthorrapha, the apical joint 
is much stouter than the rest, and may be provided with a hook-like pro- 
jection ; the distal part may be ' ringed,' or incompletely divided into a 
number of segments. In the Cyclorrapha, which includes all the blood- 
sucking Muscidae, such as Philaematomyia and Glossina, the form of 
the antenna is highly modified from the original shape ; it is composed 
of two distinct portions, the scape and the arista. The scape represents 
three basal joints. The first two of these are small and inconspicuous, 
but the third is very much enlarged and forms a conspicuous oval mass, 
which hangs down on the front of the head. It may be adorned in 
various ways, with short downy hairs or with short stout bristles, and it 
always shows on its anterior surface several 'sense pits', which, when 
seen in section, are found to be areas where the chitin is thin, and where 
there is a large accumulation of nervous tissue. In cleared preparations 
they appear as small circular clear spaces. The arista is derived from the 
terminal segments of the antenna. It is generally described as consisting 
of a single stout forwardly directed bristle, arising from the proximal end 
of the terminal segment of the scape, but a closer examination shows 
that at the junction of the arista with the scape there is interpolated 
another small joint. The arista may bear different kinds of smaller 
hairs, arranged in various ways, and its appearance is an important 
factor in classification. In Lyperosia minuta (in which three joints can be 
distinguished in the arista), there are five simple hairs arising from the 
3 



18 



MEDICAL ENTOMOLOGY 



same side, making with the termination of the central strand six equal 
filaments. In Miisca nehulo there are similar simple hairs on both sides 
of the arista. In Glossina the secondary hairs are confined to one side, 
and each of them bears a set of five or six pairs of smaller hairs, giving 
the organ a plumed appearance. The central strand of the arista is 
termed the flagellum by some authors. 

In other families of Diptera conditions intermediate between these 
are found. For instance, in the Asilidae, a family of predaceous flies 
allied to the Culicidae and the Tabanidae, the antenna consists of three 
joints like those of a Nematocerous fly, and a slender filament which 
arises from the distal end of the last segment, and projects in line with 
it ; this filament, the homologue of the arista, is termed the style. The 
complex antenna of the Muscid flies has, in fact, been evolved from the 
simple Nematocerous antenna by a concentration of the basal joints and 
an elongation of the distal. The relation of this change in form to 
the function of the parts has been discussed by Townsend. Accord- 
ing to this authority, the sense pits in the terminal joint of the 
scape are olfactory organs, and it is on account of the high degree 
of development of the olfactory sense that the third antennal joint has 
become so greatly enlarged, and has, so to speak, grown away from the 
rest of the organ. The function of the arista is to act as a sensory and 
tactile organ, for the protection of the very highly specialized third joint, 
by giving warning to the fly when it approaches obstacles. He suggests 
an interesting relation between the plumosity and the joints of the arista. 
In those forms in which the arista is plumed only on one side, the 
hairs are numerous and complex (cp. Glossina), and the small joint 
between the arista and the scape is not well developed, the arista ap- 
pearing to arise directly from the scape and to be capable of little or 
no movement. On the other hand, in those forms in which the arista is 
feathered on both sides the hairs are generally simple and comparatively 
few in number, while the joint between the arista and the scape is well 
developed, and is obviously capable of free movement. The range of 
movement of the arista will thus counterbalance the paucity of the 
sensory hairs, and a fly with a stationary arista, but with a complex 
arrangement of sensory hairs, is as well equipped as one with few hairs, 
but a wide range of movement. 

In the Pupipara the antennae are very much reduced, and are a little 
difficult to recognize. The scape consists of a single joint, roughly oval 
in shape, and enclosed in a deep chitinous pit on the surface of the head 
capsule, from which it can be partially protruded by the action of 



MOUTH PARTS 



19 



certain muscles attached at its base. There is no arista Hke that of the 
Muscid flies, but at the tip of the scape there are several stout forwardly 
directed bristles which probably represent it. The antennae and the pit 
in which they lie are of the same leathery consistence as the rest of 
the integument. 

THE MOUTH PARTS AND SUCKING APPARATUS 

It is characteristic of the Diptera that the mouth parts are adapted for 
sucking, and in the blood-sucking forms they are also modified to form a 
piercing organ. As it is through the mouth that all blood parasites must 
pass, either to or from the host, a detailed consideration of the region, 
and of the mechanism by which the parts act, is necessary. As a 
matter of convenience the first part of the alimentary canal, which is 
modified to form the sucking apparatus, will also be described here, for 
it is so intimately connected with the mouth parts both in function and 
in structure that the two cannot be satisfactorily considered separately. 

The mouth parts project beyond the head, and form a more or less 
cylindrical bundle, termed the proboscis. Its shape, relative length, and 
the position in which it is held, are of importance in systematic work. 
It may be cylindrical and of approximately the same diameter throughout, 
as in the mosquitoes, or swollen at the base and pointed distally, as in 
Stomoxys ; or cylindrical and thick with a joint in the middle, as 
in the house fly and its near allies. It may be short and inconspicuous, 
as in Simiiliiim and Ceratopogon, or very long, as in many mosquitoes. 
The position in which it is held varies from the horizontal to the vertical, 
as, for instance, in the Anopheline mosquitos and the Tabanidae. It may 
be straight or curved. In the non-biting Muscid flies, and in the genus 
Philaematomyia, it is completely retractile ; in Stomoxys and in Glossina 
only partially so. In Hippobosca almost the whole of the proboscis 
can be withdrawn within the head. 

The constituent parts of the proboscis, excluding the wall of the head 
capsule when it takes part, are enumerated as follows : — 
The Labrum, or upper lip. 

The Epipharynx, usually combined with the labrum. 
The Hypopharynx. 

The Mandibles, appendages of the fourth segment of the head. 
The First Maxillae, appendages of the fifth segment. 
The Labium, or lower lip, composed of the appendages of the sixth 
segment, fused together except at their distal ends. •- 



20 



MEDICAL ENTOMOLOGY 



Of these, the mandibles may be entirely absent, and the first maxillae 
may be represented only by their palps. In the higher Diptera a portion 
of the wall of the head capsule may be evaginated to form a part of the 
proboscis, using the term in its widest sense. 

The Dipterous mouth, highly specialized as it is, is but a modification 
of the arthropod mouth for a special mode of life, and to understand its 
structure and mechanism it is necessary to compare it with less differen- 
tiated forms. The mouth in the Arthropoda is typically a biting one, 
and is furnished with cutting jaws, the appendages of the head segments, 
with which the animal seizes and tears up its food. The jaws in the 
simplest forms are typical jointed appendages, and the mouth is adapted 
for the reception of solid particles. It will simplify the conception of 
the structure and mechanism of the Dipterous mouth if it is remembered 
that the organs which are used by even the most highly specialized 
forms are homologous with the cutting and clasping appendages used by 
the primitive insects to obtain their solid food. 

The common cockroach, Periplaneta orientalis, may be taken as an 
example of an insect with simple mouth parts; reference to the admirable 
account of this insect by Miall and Denny has already 

the"cockroach been made. The figures on Plate IV are taken from their 
book. In the cockroach all three pairs of appendages 
can be readily identified ; they all function as cutting or clasping 
weapons, and the second and third are typical jointed arthropod 
appendages. The mandibles, like those of the Diptera, are the least 
typical, and have only one joint, that by which they are attached 
to the head; the point of attachment is termed the ginglymiis. By 
means of its muscles the blade of the mandible can be moved in a 
transverse plane, till it comes in contact with its fellow of the opposite 
side. The maxillae are more complex, and consist of a number of joints. 
These are as follows: two basal joints, the cardo and the stipes, and three 
distal joints, arising about the same level from the stipes, and termed 
from within outwards the lacinia, the galea, and the palp. The shape 
and disposition of these parts is sufficiently indicated in the figures. 
As will be seen later, the maxilla in the Diptera retains the original form 
to a remarkable degree. The palp, for instance, is jointed in all but the 
highest forms, and retains its sensory character throughout. 

The second maxillae lie behind the first, and form the posterior 
boundary of the mouth. They are fused together except at their distal 
ends, and are continuous posteriorly with a membrane which occupies the 
inferior surface of the head, and merges with that of the neck. It is in 



i 



PLATE Hi 

Figure 1. Front view of head of Muscoidean fly, (half in 
diagram) much enlarged. The heavy black line 
indicates the ptilinal suture. 0 = Ocellar plate. 
FF = Frontalia. PP = Parafrontals. Pfc = Parafacials, 
CC = Cheeks. EE = Compound eyes. L = Lunula 
(postfront of larval insects). A = Antennal ridge 
(mesofront of larval insects). Fp = Mesofacial plates 
(plus facialia equals prefront of, larval insects). Fa 
Fa = Facialia. (Parts from lunula to facialia both 
inclusive taken together constitute the front of larval 
insects). Ep = Epistoma. Cl = Clypeus. PI PI = Palpi. 
Copied, with the above description, from Townsend. 

Figure 2. The facets of the compound eye of Tahanus. 

Figure 3. The head of Haematopota pluvialis, ? seen from 
the front, pg., pigment spots. These are of frequent 
occurrence in the Tabanidae, and are useful in 
distinguishing species. This is an example of a 
dichoptic fly. 

Figure 4. Scheme of the mouth parts in the Orthorraphic Diptera. 

Observe the abductor and adductor muscles of the 
mandible, ab.m. and ad.m., and the protractor and 
retractor muscles of the maxilla, p.mx. and r.mx. 

Figure 5. Scheme of the sucking apparatus in the Orthorraphic 
Diptera. 



THE PROBOSCIS 



21 



consequence somewhat difficult to decide how much of the labium is 
properly to be regarded as composed of the appendages. The two basal 
pieces are known as the submenttim and the mentiim. The latter is 
conspicuous in the elongate proboscis of the Diptera. 

The mesial constituents of the mouth apparatus are inconspicuous 
in the cockroach. The labrum is a small transverse flap which occupies 
the space between the mandibles in front, and is attached to the clypeus 
by a moveable joint. It is, in fact, a process of the clypeus, and forms 
the dorsal boundary of the mouth aperture. There is no epipharynx in 
the cockroach, and the hypopharynx is represented by a small chitinous 
fold in the floor of the mouth, on the posterior surface of which the 
salivary duct opens. 

Now it is from such a condition of affairs, both as regards structure 
and function, that the Dipterous mouth has evolved, and from a consider- 
ation of the change in habit one can deduce the changes 

which would become necessary in the structure of the "V"^ 

. \ . r T J proboscis in the 

parts, firstly, m consequence of the exchange of solid Diptera 

food for fluid, and secondly, in the case of the blood- 
sucking forms, as a result of the necessity for making a wound in 
the skin of the host. For the first a tubular channel up which the fluid 
can be sucked is essential, for the mouth parts of such insects as the 
cockroach are adapted only for the ingestion of solid particles. In the 
Diptera this is accomplished by the development, to a very high degree, 
of just those parts of the mouth apparatus which are rudimentary in the 
cockroach, namely, the epipharynx and the hypopharynx. (Plate III, fig. 5.) 
These are outgrowths, from the dorsal and ventral walls respectively, of 
the stomodaeum, * which pass forward to the level of the terminations of 
the other appendages ; the dorsal outgrowth is deeply grooved on its 
under surface, and the ventral one flattened, the two being so apposed to 
one another as to form a closed channel. The hypopharynx fulfils the 
secondary but equally essential function of conveying the saliva to the 
level of the distal orifice of the channel, in order that it may be mixed 
with the food. The labrum, which lies immediately above the epi- 
pharynx, is produced forwards and partially fused with it in order to 
strengthen the channel. The muscle at the base of the labrum, which 
in the cockroach lifts up the labrum in order to widen the mouth, is 
retained, and functions in regulating the size of the distal aperture 
between the epipharynx and the hypopharynx. 

To save confusion in the subsequent descriptions, the point at which 

* The first part of the alimentary canal. See page 26. 



22 



MEDICAL ENTOMOLOGY 



the epipharynx and the hypopharynx separate from the stomodaeum 
may be termed the mouth. The distal aperture between the epi- 
pharynx and the hypopharynx is the prestomiim. 

In addition to a channel by which the fluid food can be conveyed to 
the mouth, some apparatus is necessary to provide a sucking force. 
This is formed by a modification of the stomodaeum within the head. 
The walls of this are strongly chitinized, and are provided with muscles 
which pass between them and the walls of the head capsule ; on contrac- 
tion these muscles draw the walls of the tube apart and so produce a 
negative pressure. This causes the fluid to flow up the food channel. 

The appendages are modified for their specialized function in the 
blood-sucking forms by elongation, by the reduction of superfluous parts, 
and by the development of a suitable armature. (Plate III, fig. 4.) In the 
simpler forms, such as the mosquitoes and the horse flies, the wound is 
made by the mandibles and the first maxillae, the labium serving 
mainly as a sheath for the other appendages and the food channel. 
They are specialized into piercing stylets, elongated on account of the 
depth of skin which has to be pierced in order to reach to the level 
of blood ; the number of joints, in the case of the maxilla, is reduced to- 
ensure rigidity, and the armature and musculature are so modified as to 
be suitable for making a deep wound of narrow bore. In the higher 
Diptera the mandibles and first maxillae are not present, and the whole 
function of making the wound is transferred to the second maxillae, at 
the distal end of which there is developed a highly specialized arrange- 
ment of teeth. 

Considered with regard to their mouth parts, the blood-sucking 
Diptera fall into two well-defined classes, those in which the mandibles 
and first maxillae are present and functional, and those in which they are 
absent, and their function fulfilled by the second maxillae. These two 
classes correspond with the two sub-orders into which the Diptera are 
divided, the Orthorrapha and the Cyclorrapha. Some examples of each 
will now be described in detail. 

The proboscis of Tabaniis and of the allied genera (excluding Pan- 
gonia) is relatively short, and hangs downwards from the lower surface 
of the head. All the parts enumerated at the commencement of this 
section are present and functional. 

The mandibles (Plate IV, fig. 4) are broad flat blades of yellow 

chitin, slightly recurved on their inner edges. The cutting armature 

is limited to the distal portion of the inner edge, and 
Tabanus . r i • i-i 

consists of a row of extremely fine serrations like those 



PLATE IV 

Ij'igure 1. The first maxilla of the cockroach, x 20 

Figure 2. The mandible of the cockroach, x 2.0 

Figure 3. The second maxillae of the cockroach, pgl., 

paraglossae. x 20. These three figures from Miall 

and Denny. 

Figure 4. The mouth parts of Haentatopota pluvialis, as displayed 
by cutting off the upper and anterior part of the head 
capsule. The blade of the maxilla is omitted on the 
left side, and the palps are not drawn. The intracranial 
tunnel of the left side is shown, broken from its 
attachment to the anterior wall of the head, gy., 
ginglymus, the joint of the mandible, l.r., a strong 
flattened rod of chitin, which supports the intracranial 
tunnel at its base, and compensates for the laxity of 
the wall in the gular region, g.r., where the chitin is 
replaced by membrane. The presence of this strong 
bar is easily recognized in dissection, r., the ridge on 
which the cardo rests, cu., the cornu of the mandible, 
to which the strong adductor muscle is attached, oc.r., 
a ridge of thick chitin surrounding the occipital 
foramen. X 65. 



MOUTH PARTS : TABANUS 



23 



on a hand saw. The outer edge of the blade is thickened from the 
point upwards, and the inner in its proximal half ; at the base the 
mandible is divided into two strong cornua, the internal one of which is 
free, the external being articulated to the epicranium at a prominent 
angle. The muscles of the appendage arise in the iloor of the head 
cavity, and are inserted into the two cornua; those which pass to the 
internal cornua are the strongest, and act as adductors ; those inserted 
into the external cornua act as abductors. 

The first maxillae (Plate IV, fig. 4 and Plate V, fig. 4), as is the case in 
the cockroach, are more complex than the mandibles. Although the 
appendage is, of course, altered in form for its specialized function, all the 
parts seen in the simpler insects are present. The blade, which corresponds 
to the galea of the cockroach, is a stout chitinous rod, quadrilateral in sec- 
tion in its distal part, but flattened towards the base. It is armed with 
stout rasp-like teeth, set closely together in an imbricate manner, on the 
whole of the surface of the distal end, and for some distance on the inner 
side. All these teeth point towards the base of the blade. The blade is 
directly continuous at its base with a much convoluted piece of chitin, 
the stipes, which runs across the floor of the head at the side of the 
buccal cavity, and is attached to the wall a little in front of the occipital 
foramen by the interposition of a short stout wedge-shaped rod, the 
cardo. The lacinia is represented only by a short peg-shaped projection 
on the inner side of the base of the blade. The palp is well developed. 
It consists of two joints, a short cylindrical one and a larger conical one. 
The two palps turn a little forward from their origin, and converge 
towards one another in front of the proboscis, so as to conceal its upper 
part when looked at from the front. When the fly is feeding they are 
directed forwards, away from the proboscis. 

The muscles of the maxilla are arranged in two sets, one of which 
protracts the blade, while the other retracts it. The protractor fibres 
arise from the anterior wall of the head capsule, and pass backwards to 
be inserted into the stipes ; the retractors, which are much stronger, run 
in the opposite direction, from the neighbourhood of the occipital 
foramen. 

The method by which these appendages act in the making of the wound 
will now be evident. The mandibles are rotated inwards on their 
point of attachment to the head capsule by their adductor muscles, and 
the blades are thus drawn obliquely across the tissues. They are replaced 
in position by the abductors. The maxillae are alternately protracted and 
retracted by two sets of muscles pulling in different directions, and at 



24 



MEDICAL ENTOMOLOGY 



each retraction the barb-like teeth are drawn through the tissues. In 
each case the armature of the blade and the musculature are admirably 
adapted to one another. One might compare the action of the mandible 
to that of a circular saw cutting through a short arc, and that of the 
maxilla to a file, thrust in and out of the wound. As the wound is deep- 
ened the cutting blades are gradually lowered into it. (Plate IV, fig. 4.) 

The lahrum-epipharynx has its two constituent parts fused together to 
form a flattened spatulate slip, convex on its dorsal surface, and resembling 
a two-handed sword when seen from the front. The labral lamina is 
thinner than the epipharynx, and does not reach quite to the distal end. 
The two are only loosely united at the proximal end, where the labrum is 
attached to the clypeus by a short tongue-shaped piece, in which is 
inserted a short muscle. The epipharynx is separated from the labrum 
by a small amount of cellular tissue, and at the upper end it fuses with 
the dorsal plate of the buccal cavity, there being no suture to break 
the continuity of the chitin. Its distal end is blunt, and has on it three 
sets of minute tubercles, two lateral and one median. These are not 
cutting teeth, but have another function, which will be referred to later- 
The ventral surface is strongly concave, and forms the dorsal wall of 
the food channel. 

The hypopharynx resembles the labrum -epipharynx in shape, but is 
much thinner and more slender, and is produced to a narrower point ; the 
extreme tip, in fact, is very soft and thin. It is a little shorter than the 
labrum-epipharynx, and flatter on section. When the parts are in situ 
it closes in the gap between the two lateral edges of the groove in 
the epipharynx. At its base the hypopharynx is directly continuous with 
the ventral plate of the buccal cavity. It is pierced throughout its length 
by the salivary duct. Where it merges with the buccal cavity there is a 
small chitinous pouch, the salivary pump, on the ventral surface. (Plate 
V, fig. 1.) This is interposed between the salivary duct in the head and 
that in the hypopharynx, and is surrounded by a small fan-shaped 
muscle, by which the supply of saliva to the wound is believed to be 
regulated. (Plate V, fig. 3.) 

The labium, unlike the other mouth parts, is a soft organ, and has a 
wall composed of thin plates of chitin and membrane, enclosing a 
series of muscles and other structures. It and the palps are the only 
parts which can be seen on external examination, the other organs 
being entirely concealed in a groove on its anterior surface when the 
proboscis is in the position of rest. It is divided in its distal third 
into two labella. The wall of the labium proper is formed, on the 



MOUTH PARTS : TABANUS 



23 



posterior and lateral aspects, by a shield-shaped plate of chitin, the 
mentitm ; anteriorly there is a thin gutter-shaped plate which may be 
termed the labial gutter, in which the piercing parts rest. These two 
plates are connected together by a loose membrane passing between their 
lateral edges. The lahella are bilaterally symmetrical oval lobes, continu- 
ous with one another posteriorly, but diverging in front. Their external 
walls, continuous with the walls of the labium, are strengthened along the 
distal border by thin plates of chitin, the proximal one of which is 
indented to receive a prominent spur of the mentum, the two forming a 
loose joint. The internal walls of the labella, which are normally in 
contact with one another, are formed by a complex structure known as 
the pseiidotracheal membrane, by means of which the fly is enabled to 
absorb fluid from moist surfaces. This structure, which is of common 
occurrence in the Diptera, will be described in detail as it occurs in 
Miisca, and it will be sufficient to note here that its occurrence in Tabanits 
is in accordance with the observation often made, that these flies can 
drink water. 

The muscles of the labium lie within the cavity enclosed by the wall, 
and serve to control the position of the labella. They arise in three sets 
from the internal surface of the mentum, and are inserted into the 
internal surfaces of the chitinous plates of the labella. When all three 
sets contract at the same time the labella are diverged from one another, 
and also retracted ; by means of the anterior and posterior sets the 
fly is able to adjust the oral surfaces to the surface on which it 
wishes to feed. Retraction of the whole of the labella takes place when the 
piercing stylets are introduced into the wound ; the intrinsic muscles 
are assisted in retraction by a smaller pair inserted into two conspi- 
cuous cornua at the proximal end of the mentum. 

When the internal or oral surfaces of the labella are to be used 
for the absorption of fluid from a moist surface, the space between the 
inner and outer walls of the organ is distended with blood forced down 
from the head and body of the fly by respiratory movements. The 
details of this irnportant mechanism will be discussed with regard to 
Mitsca, but it is well to note that, in the case of Tabanits and in fact all 
the Diptera, the space enclosed by the labellar walls is continuous with the 
general body cavity. 

In the space between the inner and outer walls of the labella there is 
a labial salivary gland, which resembles that of Miisca, and need not be 
described here on that account. 

The channel between the epipharynx and the hypopharynx leads into 
4 



26 



MEDICAL ENTOMOLOGY 



the pumping apparatus, by means of which the blood is drawn up from 

the wound. It has already been stated that this is devel- 

The Sucking oped from a part of the alimentary tract within the 
Apparatus ^ ^ . 

head. To understand the true nature of the pumping 

organ it is necessary to refer for a moment to the embryology of the parts. 
The alimentary tract of insects is developed in three divisions, only 
the middle one of which is lined with true digestive epithelium. The 
anterior and posterior regions are formed by invaginations of the cuticle 
and are therefore lined with chitin which is continuous with that of the 
exo-skeleton. In most parts this chitin forms only a thin laj^er, but in 
a part of the canal within the head the walls are strongly chitinized to 
form the sucking chamber. It may be supposed that in the earliest forms 
the whole of the tube was dilated to form a single chamber, and united 
with the wall of the head capsule by means of radiating muscle fibres, 
which, by drawing the walls apart, could produce a negative pressure 
sufficient to draw up the fluid. In the course of the differentiation of 
species the single cavity became divided into two, of equal or unequal 
size, and a sphincter muscle, in some cases, developed between them. 
(Plate III, fig. 5.) 

In all the Diptera these two chambers, in one form or another, can be 
distinguished, and we may adopt for them the terms buccal cavity and 
pharynx respectively. The original circular lumen is modified, in the 
part which functions as a pump, by the moulding of the wall into two, or 
in some cases three, strong chitinous plates, normally in contact with 
one another but capable of being pulled apart by the dilator muscles. 
In the Orthorrapha there are two functional pumps, while in the 
Cyclorrapha the first is modified to form a connecting tube, without 
dilator muscles. 

In Tabaniis the two pumps are well developed. (Plate V, fig. 1.) The 
buccal cavity is an oblong chamber composed of two flattened plates of 
chitin, continuous, as previously stated, with the epipharynx and hypo- 
pharynx of the food channel. At the posterior or upper end the walls 
are produced into two stout cornua, between which the 'cavity opens into 
the pharynx by a short and narrow channel surrounded by a sphincter 
muscle. The buccal cavity, being in line with the food channel, is 
perpendicular to the long axis of the body, while the pharynx is in line 
with it, the channel between them opening into its middle portion. 
It is formed by a single quadrilateral plate of chitin, the lateral angles of 
which are turned downwards and connected with one another by a 
membrane continuous with that of the channel leading from the buccal 



PLATE V 



Figure 1. The sucking apparatus of Tabanus, schematic, in 
profile, e.b.c, a muscle with a fine tendon, attach- 
ed to the cornua of the buccal cavity on each side. 
These probably draw up the cavity, and with it the 
epipharynx and the hypopharynx, while the mandibles 
and maxillae are in action, sph., sphincter muscle, 
c.p., compressor muscles, which assist in returning the 
walls of the pharynx to a position of rest. e.L, ele- 
vator muscle of the labrum, by which the size of the 
prestomal opening is regulated. p. ph., protractor 
muscles of the buccal cavity, acting probably in 
opposition to e.b.c. r.oes., retractor muscle of the 
oesophagus. Note that the pharynx is anterior to the 
brain, while in the mosquito it is mainly posterior. 
X 40 about. 

Figure 2. Transverse section through the head of a mosquito, to 

show the arrangement of the plates of the pharynx. 

l.d.ph., the lateral dilators. 
Figure 3. The labium of Haematopota, seen in profile, in a 

cleared preparation, a.g., the groove in the anterior 

surface in which the piercing stylets are concealed. 

The membrane, mb., is continuous with that of the 

gular region. X 54. 
Figure 4. The distal end of the maxilla of Tabanus, to show the 

teeth. X 650. 

Figure 5. The sucking apparatus of Joblotia, a large mosquito. 

f.c, a flange projecting inwards under cover of the 
clypeus, to which is attached a muscle, mu., probably 
regulating the size of the prestomal slit in the act of 
sucking, by lifting up the labrum. t., the chitinous 
tube which passes through the brain and connects the 
buccal cavity and the pharynx, f., a chitinous flange 
providing attachment for the muscle which works the 
salivary pump, x 90. 



THE SUCKING APPARATUS: TABANUS 



27. 



cavity, and with the oesophagus, which opens out of the posterior end of 
the pharynx. The muscles which dilate these chambers arise from the 
walls of the head capsule. Those of the buccal cavity are inserted into 
the anterior surface of the dorsal plate, and arise from the epicranium 
below the antennae. Those which dilate the pharynx arise from the 
region of the vertex, and pass down to the dorsal surface of the pharynx; 
there are some subsidiary muscles attached to the turned down angles of 
the plate, arising in the lateral regions. 

The blood is pumped up, not by a single dilatation of the chambers, 
but by rapidly repeated ones, and the mechanism by which the plates are 
brought again into contact with one another in readiness for the next con- 
traction has now to be considered. It has been repeatedly stated, with 
reference to the similar structure in the mosquito, that the replacement of 
the plates is brought about by the natural elasticity of the chitin, but the 
process is more complex than this. The true explanation of the collapse 
of the chambers is to be found in the presence of certain large and tough 
air sacs, which surround the brain and take up a large proportion of the 
space within the head capsule ; these are in communication with the rest 
of the respiratory system of the fly. When the sucking pumps are 
dilated, room must be made in some manner for the increased contents 
of the head, and air is either forced out of these sacs into the thorax, or 
else the air in the sacs is compressed. When the cavity is to be 
emptied again, the air is either returned from the body to the sacs by 
means of the contractions of the muscles of the body wall, acting as in 
respiration, or else the positive pressure in the air sacs becomes active as 
soon as the contractions of the muscle pass off. With the collapse of the 
chamber the blood in the cavity passes backwards to the pharynx, or from 
the pharynx to the oesophagus. 

The mechanism of the mouth parts and sucking apparatus in Tahaniis 
may be summed up as follows. The fly settles down on the skin of the 
host, and by means of the tactile hairs on the end of the proboscis selects 
a suitable place. A firm hold is then taken on the skin by means of the 
claws on the feet, the labella are retracted to expose the piercing stylets, 
and are also diverged from one another so that their oral surfaces are 
applied to the skin. The mandibles and maxillae are then put in action, 
the former acting like a saw and the latter like a file, and by rapidly 
repeated movements cut a hole in the skin. Meanwhile the epipharynx 
and hypopharynx are drawn slightly upwards, by means of a pair of 
muscles which pass from the cornua of the buccal cavity to the epicranial 
wall in the region of the vertex. When the level of blood is reached 



28 



MEDICAL ENTOMOLOGY 



they are protracted. The pumping action in the buccal cavity then 
commences, the sphincter separating it from the pharynx being con- 
tracted. Immediately the cavity is full the sphincter relaxes, and the 
pharynx dilates as the blood is sucked into it from the first chamber. 
When the air pressure is in turn exercised on the pharynx the blood 
flows. into the oesophagus. 

The other blood-sucking Orthorrapha, with the exception of the mos- 
quito, which will be dealt with separately, resemble Tabanus in the 
structure of their mouth parts, the differences being 

Other Orthorraphic ^^ matters of detail. In all the proboscis is 

Diptera— Plate VI . ^ 

relatively short, and is directed downwards from the 

under surface of the head. The labium functions merely as a sheath 
for the other mouth parts, none of these forms having a pseudotracheal 
membrane like that of Tabanus. The mandibles are in each case 
flat and blade-like, with a serrated internal edge. The serrations may, 
as in Simiilitim, (fig. 6), be continued for a short distance on to the 
external margin, so that the blade cuts in abduction as well as in adduc- 
tion. The maxilla in Simulium (fig. 6) is flattened and shaped like a long 
and narrow triangle, with a simple armature consisting of a single row of 
strong recurved teeth down each edge. The blade will, therefore, cut only 
in retraction. In Ceratopogon the maxilla is stout at the base, but 
attenuated and pointed at the distal end, where it is armed with a row of 
five fine hook-like teeth, set on the inner and thinnest edge. The maxil- 
la of Phlcbotomiis (fig. 7) is stout and rod-like, and has an armature on 
two sides. On one side — it is difficult to say which, for the blade is 
very easily twisted — there is a row of minute but stout teeth extending 
from the distal extremity for a short distance, and on the other a short 
row of much smaller teeth commencing some distance from the tip. 
The first set point towards the base of the blade and will, therefore, 
cut during retraction ; the second set point towards the tip and cut 
only in protraction. In each case the blade of the maxilla becomes 
continuous at its base with the stipes, and is provided with retractor 
and protractor muscles, of which the former are always the stronger. 

In these three forms the distal ends of the labrum-epipharynx and the 
hypopharynx are modified in a highly suggestive manner. The opening 
at the prestomum is in each case a transverse slit, for the distal ends are 
always flattened and the canal between the two parts broadened out. 
In Simulium (figs. 14 and 13) the end of the labrum-epipharynx is broad, 
soft, and membraneous, and has on it two minute sets of three curved 
hooks ; on the dorsal aspect there is a row of stout and long but only 



4. 




29 



PLATE VI 



Figure 
Figure 
Figure 

Figure 
Figure 
Figure 



1. 
2. 
3. 



The hypopharynx of Cemtopogon sp. X 1200 
The labrum-epipharynx of same, x 1200 
The labrum-epipharynx of Johlotia sp. Very highly 
magnified. 

4. The hypopharynx of same. Very highly magnified. 

5. The maxilla of same, x 630 

6. The labrum-epipharynx of Tabanus albiiiieclius, dorsa] 
view. X 600 

Figure 7. The cutting edge of the mandible of Simiiliiim indiciim, 
X 1000 

Figure 8. The hypopharynx of same. X 630 
Figure 9. The labrum-epipharynx of same. The lateral hairs 
are very much finer than represented in the drawing. 

X630 

Figure 10. The maxilla of same, side view. X 1000 
Figure 11. The labium of Phlehotoinus papatasi, seen from 
behind. 

Figure 12. The mandible of same, distal end. 

Figure 13. The maxilla of same, showing the two sets of teeth. 

Figure 14. The mandible of same. 

Figure 15. The maxilla of same, showing the ' apodeme,' or 

representative of the stipes. 
Figure 16. The labrum-epipharynx of same. 
Figure 17. The hypopharynx of same. 

Figure 18. The head of same in side view, showing the proboscis, 
pro., and the long palp. 
Except in figures 11, 15, and 18, only the distal ends are shown. 
Figures 11 to 18 are frorn Grassi, copied by Mr. G. Taylor, 



MOUTH PARTS : MOSQUITO 



29 



faintly pigmented hairs, on each side of the canal. The distal border of 
the hypopharynx is split up into a row of innumerable elongate processes, 
which give it the appearance of a frayed piece of cloth. In Ceratopogon 
(figs. 1 and 2) both organs have indented margins, with five processes 
produced distally between the notches ; the labrum-epipharynx is the 
broader organ of the two, so that its processes overlap those of the 
hypopharynx. 

In Phlebotomits the two parts of the food canal are more pointed at 
their distal ends. The borders of both are split up into fine tooth-like 
processes, those on the hypopharynx being much smaller and rnore 
numerous than those on the epipharynx. The significance of these 
' teeth ' will be discussed when the parts in the mosquito have been 
described. 

In each of the above flies the two sucking chambers are well devel- 
oped and functional. In Simiiliiim the buccal cavity is like that of 
Tahanus, while the pharynx is composed of three plates, like that of the 
mosquito. The two are, as in Tabamis, placed perpendicular to one 
another. In Ceratopogon the buccal cavity is also composed of two 
plates, dorsal and ventral, but it is smaller, and does not appear to take 
as much part in the sucking operation as the pharynx ; this is also 
composed of two plates, and resembles the buccal cavity, to which it is 
inclined at about half a right angle. In Phlebotomiis the buccal cavity, 
which resembles that of the others, is small ; the pharynx is the more 
important sucking chamber, and is composed of three chitinous plates. 

The mosquito represents an extreme type, characterized by great 
elongation of the mouth parts, reduction in the size of the buccal cavity, 
and a corresponding increase in the size of the 
pharynx. The elongation of the mouth parts is accom- ''"''p|''''°^'''yi'*°~ 
panied by a reduction in the transverse diameter, 
specially noticeable in the labium. 

In the Anopheline mosquitoes the proboscis is held straight in front of 
the head in the position of rest, while in the other genera it is inclined 
downwards. The position in which it is held in the act of feeding is, 
however, the same in the two forms, namely, perpendicular to the long 
axis of the body, or nearly so. 

The mandibles (figs. 1 and 3) are extremely slender slips of chitin, armed 
only at their distal ends. In sections the blade appears concave on its 
inner surface, and is closely pressed against the hypopharynx. At the 
tip, in the case of Anopheles, Xhe blade is broadened out a little, and has a 
short .row of extremely fine serrations. In many species, of ,C«/ex the 



30 



MEDICAL ENTOMOLOGY 



teeth on the mandible cannot be distinguished at all. At the base the 
blade is broader and stouter, and turns sharply outwards at its articu- 
lation with the head ; the muscles attached to it are small, and the 
mandible does not appear to play an important part in the cutting 
operation. Mandibles are absent in the male, and the whole appendage 
may be regarded as a retrogressing one. 

The maxillae (figs. 1 and 2), slender though they are, are stouter than 
the mandibles. On section the two blades are seen to form a concavity 
on which the hypopharynx rests. When mounted flat the blade 
is seen to have one edge thick and rounded, and the other extremely 
sharp and attenuated ; the surface between the two edges is divided into 
a number of separate areas by means of transverse lines, which produce 
slight indentations where they meet the thinner edge. At the distal 
end there is a single row of short conical teeth, arising from the thin edge. 
The number of these differs in different species, but is usually from ten 
to twenty. At the base the blade merges into the stipes, which has often 
been described as the ' apodeme ' of the maxilla. The retractor muscles 
attached to it are much more powerful than the protractors. The palps, 
which vary in length and in the number of joints in the diff"erent genera, 
and are of importance in classification, are attached to the base of 
the blade where it merges with the stipes ; as in the other forms, they are 
held out in front, away from the proboscis, when the mosquito is feeding. 

In some of the larger mosquitoes the blade has a much more formidable 
cutting apparatus than the one just described. In a species of Johlotia 
(fig. 7) there are three sets of teeth. One set resembles that seen in 
Anopheles, and does not extend quite to the tip of the blade ; these teeth 
are only slightly recurved, and can probably cut in both directions, though 
most efficiently in retraction. Distal to them and on the same border 
there is a row of much finer and sharper teeth, which point towards the 
tip, while at the extreme end of the blade, distal to the others, there is a 
row of stout but minute teeth like those on the maxilla of Tabaniis, ex- 
tending on to both surfaces of the blade. Such a weapon will cut both 
in protraction and in retraction. 

The labniin-epipharynx is not flattened as in the other forms, but 
rounded. The constituent parts are more closely fused together, and 
there is very little loose tissue between them. The epipharynx takes the 
greater part in the formation of the stylet, and is produced beyond the 
labrum. The distal end( Plate VI, fig. 3) is in most genera obliquely 
truncated in such a manner as to resemble a J pen, and is incised in the 
longitudinal direction, the portions of the margin between the incisions 



MOUTH PARTS : MOSQUITO 



31 



projecting as minute ' teeth '. There is usually a well marked central 
split. At the base the epipharynx and the labrum separate, the former 
fusing with the buccal cavity, the latter projecting within the cavity of 
the clypeus, which in the mosquito is always prominent. 

The hypopharynx (figs. 1 and 4) is an extremely delicate flattened 
slip, perforated throughout its length by the salivary duct. It falls a little 
short of the other mouth parts, and has a soft distal end. (Plate VI, fig. 11.) 

The labium (fig. 1, and Plate VI, fig. 4) is a long, narrow, and flexible 
chitinous tube, hollowed out on its anterior surface for the reception of 
the piercing parts. The greater part of its wall is formed by the mentum, 
which forms the posterior and lateral sides, and arches inwards across 
the groove. The anterior surface is completed by membrane, forming a 
labial gutter which is depressed below the lateral margins. In the space 
enclosed by the mentum and the labial gutter there are several muscles, 
some tracheae, and a few free cells ; some of the latter belong to the 
haematocoele, for the cavity of the labium is in communication with the 
rest of the body cavity. At its distal end the labium is divided into two 
small labella, which are articulated to the rest of the organ by a definite 
joint formed by small chitinous rods. The distal margin of the labellum 
has on it many fine sensory hairs. There is no pseudotracheal mem- 
brane, but delicate longitudinal grooves can be made out on the inner 
surfaces of the lobes. At the proximal end the wall of the labium 
becomes continuous with the membraneous area at the inferior surface of 
the head. 

The movements of the labium are the same as those in Tabaniis. 
The intrinsic muscles, which are easily seen in cross sections, are 
inserted partly into the chitinous rods which form the joint between 
the labium and the labella, and partly into the lower end of the mentum. 
When the insect commences to feed the labella are applied to the surface 
of the skin, and diverged from one another so that their oral surfaces are 
in contact with it. The piercing stylets are then thrust into the skin 
between the two labella, which act, to use Nuttall and Shipley's expres- 
sion, like the fingers of a billiard player in guiding the cue. As the 
chitinous stylets enter the skin, the labium is bent backwards, the labella 
retaining their position. The bending is in consequence of the dispropor- 
tion in the length between the labium and the free portion of the stylets, 
but it is not produced by mere mechanical displacement. The upper end 
of the mentum is not a uniform sheet of chitin, but is broken up into a 
number of minute elongate transverse plates set closely side by side, 
with membraneous interstices, an arrangement which enables it to bend 



32 



MEDICAL ENTOMOLOGY 



readily when the muscles which traverse the labium in its long diameter 
contract. In a mosquito in the act of feeding the labrum-epipharynx can 
be distinguished with the aid of a lens, passing directly from the head 
into the wound, and widely separated from the labium, the upper part of 
which is bent sharply backwards. 

The sucking apparatus of the mosquito (Plate V, fig. 5) differs from 
that of any of the flies so far considered in several important particulars. 
The first sucking chamber is very small, and takes only a minor part in 
the mechanism, while the pharynx is very well developed, the two being 
connected by a stout chitinous tube of considerable length, instead of a 
short membraneous duct. It should be noted that the pharynx of the 
mosquito is not, strictly speaking, homologous with that of Tabanus, for 
it is situated mainly behind the brain, instead of anterior to it. Their 
true relation will be evident from what has been said with regard to the 
development of the sucking chambers. 

The buccal cavity lies below the clypeus, and commences by the fusion 
of the two edges of the groove in the epipharynx, the upper lamina 
of the hypopharynx uniting with the tube so formed ; it terminates at 
the level of the posterior border of the clypeus, running upwards and 
backwards, not quite in line with the food channel. Its lumen is 
transverse in the anterior part, and circular posteriorly. The ventral 
wall is the thicker of the two, and is chitinous throughout. The dorsal 
wall is chitinous in front and behind, but has a membraneous area in the 
middle portion. The muscles which dilate the cavity are inserted into 
its dorsal wall, and arise from the internal aspect of the clypeus. 

There is a curious structure, a part of the salivary apparatus, attached 
to the anterior end of the ventral plate of the buccal cavity. (Plate V, 
fig. 5.) It consists of a small cup-shaped receptacle, with the open end 
directed posteriorly, and covered by a tough membrane which is 
pierced in its centre by the salivary duct coming from the thorax. The 
closed anterior end communicates directly with the salivary duct in 
the hypopharynx. Where the duct enters the membrane there are 
several chitinous spicules, and to these are attached delicate muscle 
fibres, which arise from a pair of prominent flanges at the posterior end 
of the ventral surface of the buccal cavity. According to Nuttall and 
Shipley the function of this structure is to pump the saliva from the 
thorax. The contraction of the muscles produces a negative pressure in 
the receptacle, the elastic rebound of the membrane forcing the saliva 
outwards. 

The pharynx of the mosquito is mainly posterior to the brain, and is 



PLATE VII 



Figure 1. The head and mouth parts of Ctilex fatigans, in side 
view. X 43 

Figure 2. The dista! end of the maxilla of same. \'ery highly 
magnified. 

Figure 3. The distal end of the mandible of same. Very highly 
magnified. 

Figure 4. A cross section of the labium of same, showing the 
mouth parts in the resting position, l.g., the labial 
gutter, connected to the mentum by the membrane, 
mb. ha., haematocoelic space, always exaggerated in 
sections on account of the shrinkage of the parts. The 
space is in continuity with the haematocoele of the 
head and body, hy.c, hypodermal cells, mu., the 
longitudinal muscle of the labium, which functions in 
retracting it when the piercing stylets enter the wound. 
The labium is bent very much as a bow is bent when 
the bowstring is tightened, x 1000. 

Figure 5. The mandible and maxilla of same dissected out in a 
cleared preparation. The mandible is separated from 
its attachment, x 170. 



t 
I 

I 



SUCKING APPARATUS OF MOSQUITO 33 



separated from the buccal cavity by a considerable distance, the interval 
being bridged over by a chitinous tube, which merges at the two ends 
with the sucking chambers. This tube is arched with its concavity down- 
wards, the amount of curvature depending upon the angle at which the 
proboscis is held. In the Anopheline mosquitoes it is only slightly curved, 
while in Culex, in which the buccal cavity and the pharynx are inclined 
to one another at a considerable angle, the curvature is very marked. 
The pharynx, when seen from the side, is a pear-shaped organ, 
continuous by its narrow end with the above tube. It is composed of 
three chitinous plates, two lateral and one dorsal, attached to one 
another by membraneous intersections. Each plate is curved in cross- 
section, with the convexity directed inwards, and in the resting condition 
the three are in contact with one another, so that the lumen is 
triradiate. To each of the plates a strong dilator muscle is attached 
(Plate V, fig. 2), those of the lateral plates arising from the sides of the 
head cavity behind the eyes, and those of the dorsal plate from the 
epicranium in the region of the vertex. When the muscles contract the 
plates are pulled apart, and the lumen made more or less circular. 

At the point where the buccal cavity ends and the tube which connects 
it with the pharynx begins there is, in Anopheles, a distinct angle, and at 
this point there are on the internal aspect of the ventral plate a number 
of stout hairs of peculiar form, described in detail by Annett, Button, 
and Elliot in Anopheles costalis. It is stated that these structures, aided 
by the angling of the tube, function as a valve. 

At the posterior end of the pharynx the chitinous plates are marked by 
numerous longitudinal ridges, which project on the internal surface as 
small tubercles. These are adorned with clusters of fine hairs, which, 
according to Nuttall and Shipley, act as strainers in separating the coarse 
particles from the food. Where the pharynx is narrowed to become 
continuous with the oesophagus there is a well developed sphincter 
muscle. 

It will be noted that the buccal cavity in the mosquito is so much 
smaller than the pharynx that it cannot possibly draw up enough blood 
to fill the later, and that there is no sphincter muscle between them. 
Probably the chambers dilate together, communication with the aliment- 
ary tract being shut off by the sphincter muscle posterior to the pharynx. 

The reader may remark, in the foregoing account of the mouth parts of 

the Orthorrapha, and especially with regard to the 

• ^ r .1 1 • Mechanism Of the 

mosquito, that the account of the mechanism is some- gj^j^g apparatus 

what different to that usually put forth, The motive 

5 



34 



MEDICAL ENTOMOLOGY 



force by which the puncture is made is usually ascribed, somewhat vaguely, 
to the forward thrust of the body. To put this in more precise 
terms would be to assert that the muscles of the legs thrust the body 
forward, and that this force is conveyed to the piercing stylets through 
the neck. There are two reasons why this cannot occur. In the first 
place,, the neck is anatomically incapable of conveying such a thrusting 
force, being in most cases almost entirely membraneous ; and even 
if it could do so, the force would have to act through an angle 
which is often nearly a right angle, for the proboscis is not directed 
in line with the body in the position of action, but perpendicular to 
it. Even the Anopheles mosquito bends its proboscis downwards when 
it is in use, thus losing any advantage its forwardly directed pro- 
boscis might be thought to have. The making of the wound is there- 
fore to be regarded as a function of the appendages, acting by their own 
muscles, exactly as do the appendages of other arthropods. It might, on a 
first consideration, be difficult to believe that such minute lancets, actuated 
by what are after all extremely minute muscles, are capable of making a 
wound sufficiently deep to draw blood, but the mechanical difficulties 
are less than they seem. In the first place, one has to remember that 
rapid contraction is a special characteristic of insect muscle ; according 
to Marey, the wing of a fly can make 330 contractions per second. 
If it is admitted that the muscles of the appendages can contract at 
anything approaching this rate, it is easy to understand how the stylets 
enter the skin. There is, moreover, no waste of effort, for a deep 
wound of narrow bore is all that is required, and the stylets are elongate 
and narrow, having a short and sharp cutting edge. In the second place, 
the shape and thinness of the stylets does not render them as liable to 
fracture as one might suppose, for they possess a certain amount of 
flexibility, probably sufficient to enable them to bend if they meet with 
any resistant tissue when they are thrust in. As the maxillae, which 
would appear to be the most liable to this sort of injury, cut mainly in 
retraction, the stress will tend rather to straighten than to bend the 
blade. Resistance met with during protraction would bend the blade, 
but no great resistance is likely to be met with at this part of the 
cutting action, for the majority of the teeth are always directed towards 
the base of the appendage. 

The labrum-epipharynx and the hypopharynx are commonly included 
with the mandibles and first maxillae as piercing stylets, and the 

^. _ processes on their distal ends are regarded as teeth. 

The Prestomum ^ . ° 

It is most improbable that they take any part in the 



THE PRESTOMUM IN THE ORTHORRAPHA 35 



making of the wound, and it seems certain that the ' teeth ' at their 
distal ends fulfil an entirely different purpose, namely, that of preventing 
particles too large for its lumen from entering the food canal, a function 
which would be in keeping with what we know of the nature and origin 
of these organs. In none of the Orthorraphic biting flies are the pro- 
cesses in the least like the cutting edges or teeth found elsewhere in 
the Diptera. They are, on the other hand, with the single exception 
of the hook on the labrum-epipharynx of Simulium, mere processes 
of no greater thickness than the margin from which they arise. 
There are no muscles attached to the bases of these organs which 
could effectively impart to them an in-and-out thrust, and any lateral or 
rotatory movement is anatomically impossible. Moreover, both organs 
fall a little short of the terminations of the appendages. There are, 
it is true, some muscles, most easily seen in Tabanus, which may 
retract and protract the buccal cavity, but the utmost limit of pro- 
traction cannot bring the terminations of the epipharynx and the 
hypopharynx to the level of the other cutting points, and indeed it seems 
more likely that the buccal cavity, and with it these outgrowths, are 
retracted during the making of the wound, and subsequently thrust down 
when the level of blood is reached. It should be noted that the only 
chitinous connection between the labrum-epipharynx and hypopharynx 
is through the thin slip of chitin by which the labrum is articulated to 
the clypeus, a condition of affairs which renders it most unlikely that 
these organs can make any effective thrust. 

When the food channel of either Simulium, Cemtopogon, or Phlebo. 
tomus is examined from the side with the parts in situ, it is found that 
the flattened distal ends of the organs are separated from one another by 
a small interval. The processes on the distal margins are directed 
across this interval, and those of the two organs come in contact. The 
opening at the prestomum is therefore guarded by an arrangement which 
resembles, and presumably acts as, a sieve, preventing the ingress of 
large particles. The size of the aperture can be regulated by the 
contractions of the muscle at the base of the labrum. 

In Tabanus the mechanism appears to be somewhat different. 
The distal end of the labrum-epipharynx is much broader and stronger 
than that of the hypopharynx, and in the normal condition of the parts 
the hypopharynx falls a little short of the termination of the former. 
The dorsal boundary of the prestomum is thus strong and rigid, while 
the ventral one is comparatively soft. When the ends of the organs 
are in a layer of blood, therefore, the latter must enter the canal from a 



36 



MEDICAL ENTOMOLOGY 



direction posterior to the prestomum ; it cannot enter from the front 
without passing through the tubercles at the tip of the epipharynx, 
for these are considerably distal to the prestomum, and would in any 
case separate out any coarse particles. Now when there is a negative 
pressure in the food canal the soft tip of the hypopharynx will be drawn 
towards the epipharynx, and the size of the opening diminished, while 
on the other hand it can be increased by the withdrawal of the labrum 
by means of the muscle at its base. There is thus a balance maintained 
between the size of the opening on the one hand and the pressure in 
the canal on the other, and should any large particle impinge on the end 
of the food channel it can be at once excluded by the valve-like action 
of the tip of the hypopharynx. 

In the mosquito the mechanism is similar. Here again the tip of the 
hypopharynx is soft (this is readily seen if fresh preparations are 
examined under a high power) and falls a little short of the tip of the 
epipharynx. Both organs are flattened at the tip, so that although the 
food channel between them is circular, the prestomum is a transverse 
slit, which can be closed by the pressure of the soft end of the 
hypopharynx against the more rigid epipharynx. 

The structures in the buccal cavity and in the pharynx which have 
been described as sieves are of very doubtful function. It is difficult to 
see how the fly could get rid of a large particle which had once got so 
far ; the only conceivable method would be a reversed peristalsis, which 
is most unlikely to occur. 

Some such filtering mechanism as this would seem to be a necessity 
for the fly, when one considers that the wound is made partly by the 
rasp-like blades on the maxillae, which tear through the tissues, and are 
very likely to loosen or dislodge particles of greater diameter than that of 
the food canal. 

In the Cyclorraphic Diptera the mouth parts are much more differ- 
entiated from the primitive arthropod type than in the forms so far 
considered. The mandibles and first maxillae are 

The Cyclorraphic absent, and the whole function of obtaining food is 
Diptera . 

transferred to the second maxillae, which have in con- 
sequence undergone profound changes. All that remains of the other 
appendages is a pair of simple palps. In the non-biting flies the inner 
surfaces of the labella are modified to form a pad by which fluid can 
be sucked up from moist surfaces, while in the biting forms, for which a 
cutting apparatus is necessary, a complex arrangement of teeth is deve- 
loped in the same situation. The external appearance of the proboscis 



THE PROBOSCIS IN THE MUSCIDAE 



37 



is further altered as a result of the protrusion of a part of the wall of 
the head capsule, containing the pharynx, to form a part of the pro- 
boscis, using the term in the wider sense. 

As the question of the origin of the blood-sucking Muscids has arisen 
in connection with the phylogeny of the parasites which they and their 
non-biting allies may harbour it will be well to refer briefly to it here. 
It will also render the somewhat complex structure and mechanism of 
the parts more easy to explain, if they are looked at from the compara- 
tive point of view. 

The relations between the mouth parts of the Orthorraphic flies and 

those of simpler insects, such as the cockroach, have already been pointed 

out, and the argument may be taken up at the point 

T ,- 1 , Origin of the Blood- 

reached with Tabanus. In this insect not only are the s„g|,i„g Muscidae 

mandibles and first maxillae present and functional, 
but the labium has assumed a function not found in other flies of 
the same group. The inner surfaces of the labella are provided with a 
complex arrangement of grooves, by means of which the fly can and does 
suck up moisture from surfaces, exactly as does Mttsca. The form may 
be regarded, in fact, as having arrived at the parting of the ways, so far 
as its method of feeding is concerned. With such a condition of 
the mouth parts two courses of evolution suggest themselves. Either 
the fly may remain a blood-sucker, obtaining its food from a wound 
made by the mandibles and first maxillae, retaining the pseudotracheal 
membrane as an accessory structure, or perhaps losing it altogether ; 
or it may come more and more to use its oral lobes, and to depend 
on them for obtaining the whole of its food, so that in course of time 
the piercing parts disappear. This is what appears to have occurred in 
the production of the Muscid type of proboscis, now found in a very 
large number of genera. 

The blood-sucking Muscids present no points in common with the 
blood-sucking Orthorrapha, but are evidently closely related to the 
non-blood-sucking Muscidae, as shown by their other characters. 
It is clear from the study of the minute structure of the proboscis 
that the assumption of the blood-sucking habit has occurred subse- 
quently to the loss of the mandibles and first maxillae. The 
essential cutting weapons are new structures, having their origin in 
the inner walls of the labella, as minute chitinous processes. In 
Musca domestica and its allies they appear to be sufficiently strong to 
act as scraping teeth, capable of scratching a surface from which a 
fluid food will exude ; in one or two other species known they are 



38 



MEDICAL ENTOMOLOGY 



perhaps powerful enough to scrape off the dried clot from a raw surface, 
to enable the fly to get at the serum and blood underneath. In those 
flies which are now confirmed blood-feeders the teeth have become 
powerful cutting weapons, and there is a specialization of the joints 
and muscles of the proboscis in conformity with their increased size. 
The whole proboscis, in fact, becomes altered in the direction of the pro- 
duction of a piercing stylet. The course of the development of this 
form of cutting apparatus can be traced with remarkable clearness in 
the present day forms, as will appear from the subsequent descriptions. 

In view of these relations, the structure of the proboscis of Mtisca 
must be understood before passing on to the blood-sucking Muscids. 
The domestic species of Miisca are moreover of sufficient im- 
portance to the sanitarian as the possible transmitters of disease to 
warrant a detailed description of their mouth parts, especially since 
there is reason to believe that it is mainly through the proboscis, 
which may be transferred from infected material to the food of 
man very frequently, that infection is conveyed. At the same time it 
should be noted that there are many species of Musca, which, although 
they have no biting mouth parts, are confirmed blood-feeders, and are 
theoretically as capable of transmitting pathogenic parasites as are true 
biting flies. These will be dealt with in Chapter III. The follow- 
ing description refers specially to Musca nebtilo, the common bazaar fly 
of Madras, but the differences between species of like habit are so small 
that it will apply to most of them. 

The proboscis of Musca, in the position of extension, hangs directly 
downwards from the lower surface of the head, and is roughly cylin- 
drical and blunt pointed. It consists of three parts, 

Musca (Plate VIII 

named from above downwards the rostrum, haustellum, 
and the labella. Of these the two latter correspond to 
the proboscis and labella of the Orthorraphic flies. The rostrum, on the 
other hand, is a part of the head cavity, which can be protruded at 
will ; it contains the pharynx and the buccal cavity. 

The proboscis is completely retractile, and when not in use is with- 
drawn ; the rostrum, reduced in size by the collapse of the air vessels 
which it contains, passes back into the head cavity, and the haustellum 
with its labella is concealed on the inferior surface. 

The rostrum is shaped like a truncated pyramid, with the narrow end 
directed downwards. Its wall consists of a tough but flexible membrane, 

which is attached above to the margins of the epistomal 
Rostrum -11 11 r 1 

orifice, and is continuous below with the walls or the 



REFERENCE LETTERS, PLATES VIII TO XIII. 



Lettering used more than once is given here. The remainder 
will be found in the descriptions of the plates. 



a. a. Anterior arch. 

a. mu. Anterior and median set of inusrles. 
ap. Apodeme of the labrum. 

axp. ' Axial apophysis. 

b. Bulb. 

b. c. Buccal cavity, 

cl. Clypeus. , 

d.ph. Dilator muscle of the pharynx, 

d. s. Discal sclerite. 

eXi h. Extensor muscle of the haustellum. 

f. Fork of the mentum. 

f. ch. Food channel, formed by the labrum-epipharynx and 

the hypopharynx. 

fl. Fulcrum, 

fu. Furca. 

hy. Hypopharynx. 

k. Keel of the labial gutter. 

1. ep. Labrum-epipharynx. 

1. gl. Labial gutter. 

1. r. Lateral rod of the labial gutter, 

lb. r. Labellar rod. 

Ibl. Labellum. 

mb. Membrane, 

mt. Mentum. 

oes. Oesophagus, 

p. Palp, 

p. b. Petiolated blade, 

p. c. Posterior cornu of fulcrum, 

p. m. Pseudotracheal membrane, 

p. mu. Posterior and lateral set of muscles, 

p. s. Pseudotrachea. 

ph. Pharynx. 

r. h. Retractor muscle of the haustellum. 

r. h. p. Posterior retractor of the haustellum. 

r. r. Retractor of the rostrum. 

rd. h. Rod-like hairs. 

si. d. Salivary duct. 

si. V. Salivary valve. 

t. Prestomal tooth. 

t. mu. Transverse set of muscles. 

rr. Trachea. 



PLATE VIII 



Figure 1. The proboscis of Mvsca iiebiilu, diagramatic, in side 
view. 

The part above b.c, and including it, is the rostrum. 
The haustellum extends from this to d.s. The rostrum 
is rotated backwards and upwards in retraction, on the 
fixed point formed by the approximation of a.a. to cl., 
the part being at the same time drawn up by r.h.p. 
w.r., the membraneous wall of the rostrum. A portion 
of the side wall of the fulcrum has been removed to 
show the position of the dilator muscle of the pharynx. 
The oral lobe of one side is seen from the inner 
aspect, c.c, collecting channel, e.w., a part of the 
external wall of the labellum, cut short. 

Figure 2. Two isolated rings from a pseudotracheal channel. 

Figure 3. A pseudotracheal ring m situ, showing the bifid end, b., 
with its attached membrane, and its flattened end, f. 

Figure 4. The arrangement of the free ends of the rings at the 
open side of the pseudotracheal channel. Bifid ends and 
flattened ends alternate. The last three figures, which 
are of Calliphora eryfJirocephala, after Graham- 
Smith. 

Figure 5. One of the prestomal teeth of Pliilaeniatoniyia guriiei. 

Figure 6. The distal end of the labial gutter of Philaematomyia 
insignis, showing the thickened lateral portions which 
articulate with the discal sclerite. x 150. 

Figure 7. The labella of Lyperosia niiniita, in the position of 
action. Drawn from a preparation fixed without clear- 
ing. The direction in which the teeth and connected 
structures lie is the reverse of that in the resting position, 
m.b., the marginal bristles, which in the resting position 
form a fringe at the distal end of the proboscis. 
Compare figure 7, Plate XIII. 

Figure 8. The teeth and connected structures of Pliilaematomyia 
insignis. The pseudotracheal channels are not 
shown. X 500. 



MUSCA— THE FULCRUM 



39 



haustellum. The palps, which are composed of a single joint, are attached 
to its anterior surface; when the proboscis is extended for use they are 
directed straight forward. Within the rostrum there is a strong chitinous 
structure known as the fulcrum, which contains the pharynx of the 
fly ; this occupies the greater part of the rostrum. The pharynx 
within it is connected with the food canal in the haustellum by means 
of a small chamber, the homologue of the buccal cavity in Tahanus. 
In addition to these structures, the rostrum contains certain important 
muscles and air sacs, and the salivary duct. 

The fulcrum (Plate VIII, fig. 1), to use Kraepelin's simile, resembles a 
Spanish stirrup iron ; the foot plate being posterior, and the toe at the lower 
end. The posterior plate is oblong, concave forwards in both diameters to 
a slight extent, and produced at the upper end into a pair of conspicuous 
lateral cornua. At the lower end it is narrowed in the transverse diameter 
and broadened out a little in the antero-posterior, so that it appears some- 
what funnel-shaped. The lateral plates, corresponding to the high sides 
of the stirrup, are triangular, and are continuous with the sides of the 
posterior plate. Their free superior and anterior sides are deeply incur- 
ved, the curvature on the latter being interrupted by a sharp spine, which 
projects downward and forward in the lower third. These two lateral 
sides are connected with one another in front by a transverse arch, which 
passes between their anterior angles ; this corresponds to the part to 
which the stirrup leather would be attached. It is roughened and 
thickened for muscle attachment. The anterior arch of the fulcrum is 
continuous with the membrane which forms the anterior wall of the rost- 
rum, and can be seen in fresh specimens when the proboscis is extended. 

The posterior plate of the fulcrum, as above described, is the ven- 
tral wall of the pharynx. Anterior to it there is a thinner plate of 
a corresponding size, which, in the resting condition, is closely ap- 
posed to it, and forms the dorsal wall of the cavity (Plate X, fig. 4). It is 
traversed down the middle line by a thick and rough ridge, to which most 
of the dilator muscles are attached. At the upper end the two walls of 
the pharynx merge to form the oesophagus, while at the lower end they 
are connected with the walls of the buccal cavity by a short membrane. 
The space between the lateral walls of the fulcrum is occupied by the 
dilator muscles of the pharynx, which pass from the anterior arch and 
the adjacent membrane to the ridge in the middle line of the dorsal wall 
of the pharynx. When these muscles contract the two plates are drawn 
apart, and the fluid food is drawn up into the cavity of the pharynx, 
exactly as in Tahanus. 



40 



MEDICAL ENTOMOLOGY 



The buccal cavity lies partly between the projecting lateral portions of 
the lower end of the fulcrum. It is a small chamber, formed by a single 
triangular plate of chitin, the apex of which points downwards, the 
lateral angles being turned forwards and inwards towards one another 
and connected by a membrane. Distally the cavity is in communication 
with the food canal in the proboscis, in a manner which will be described 
presently. The buccal cavity has no dilator muscles, and plays only a 
passive part in the mechanism of feeding. 

The haiistellum consists of the labrum-epipharynx, the hypopharynx, 

and the labium, the latter being divided distally into two labella. 

Mandibles and first maxillae are absent. The two 
Haustellum , • , r , , ■ , , , • 

organs which torm the suckmg tube are concealed m 

the groove on the anterior surface of the labium, which alone can be 
seen without dissection. 

The labrum-epipharynx (Plate IX, fig. 1), when seen from the front, is 
shaped like a blunt arrow head. It is a much softer organ than that of 
Tabanus, being composed of much thinner chitin, and having more 
cellular tissue between the two parts, which are readily distinguished 
from one another. The labrum gives its shape to the organ, and forms 
the anterior and lateral sides, and the external thirds of the posterior 
surface. Where it is deficient in the middle line of the posterior or 
ventral surface there is a deep chitinous gutter, the epipharynx, connect- 
ed to the edges of the labrum by a short strip of membrane. The 
distal end of the organ is flattened and tongue-like, and has on its ventral 
surface several conspicuous sensory tubercles. Between the two walls 
there is a series of fan-shaped muscles, arising from the internal surface 
of the labrum and inserted into the epipharynx. 

At the upper end the two parts separate from one another. The la- 
brum becomes continuous with the anterior wall of the rostrum, which is, 
of course, continuous above with the clypeus. The epipharynx projects 
a little distance into the rostrum, and is connected with the anterior wall 
of the buccal cavity by a short membraneous fold. 

The labrum is provided with a pair of apodemes, which lie within the 
rostrum, and are articulated to the labrum at its broad upper end. These 
are stout sinuous rods of heavily pigmented chitin, pointed at the lower 
end, and with a short barb-like projection just above the point. Their 
ends are received into a pair of small pits in the labrum. The upper 
ends of the apodemes are flattened and broadened, for the insertion of a 
pair of powerful muscles. 

The hypopharynx is a soft tongue-shaped organ, rather shorter than 



MUSCA: LABIAL SALIVARY GLAND 



41 



the labrum-epipharynx, and is rather broader in its transverse than in its 
antero-posterior diameter ; its lateral borders are produced a little for- 
wards so as to come better into apposition with the epipharynx. Its 
proximal half is closely fused with the anterior surface of the labium, 
a feature which is generally found in the non-biting flies, for it is only 
when the saliva has to be injected into a wound that the hypopharynx 
becomes free. The salivary duct perforates the whole length of the 
hypopharynx in the usual manner, as in Tahaniis. At the upper end the 
hypopharynx projects into the rostrum posterior to the epipharj-nx, and 
is attached in a similar manner to the membraneous wall of the buccal 
cavity. 

The labium is roughly cylindrical in shape, broader in the middle 
than at the two ends, and a little flattened on the anterior surface. Its 
wall is composed of two plates of chitin, united by a loose membrane. 
Of these by far the larger is the mentum, an oblong plate, concave on 
its anterior surface, which forms the posterior and part of the lateral 
walls. On the anterior surface there is a very thin and narrow plate of 
chitin, depressed below the rest of the surface, and united in its upper 
half with the hypopharynx. On either side of this there is a thin but 
rounded rod of chitin, the two forming the boundaries of the shallow 
groove in which the labrum-epipharj-nx and the hypopharynx lie. These 
rods take an important part in the articulation of the labium with the 
labella. 

Within the cavity of the labium there are the intrinsic muscles which 
move the labella, and the labial salivary gland. The latter is similar to 
that found in Tahanus, and to that of Philaematom- 
yia. It is situated at the lower end of the labium, '"^'"^Gla^'d'*''^ 
at the point where it divides into the two labella, 
and consists of a rounded mass of large cells, averaging about forty 
microns in their long diameter, spherical or oval in shape, and closely 
compressed together. They lie oear the anterior surface of the labium, 
and have their narrow ends directed towards the surface. The proto- 
plasm is finely granular, and contains usually a single large nucleus, 
occasionally also an additional small one. At one side of the nucleus 
there is a permanent vacuole, generally cresentic in outline, and lined by 
a clear non-staining layer said to consist of chitin. The cells communi- 
cate with the exterior by means of fine ducts which arise intracellularly, 
and unite to form a single channel on each side, opening at the side of 
the oral pit. The secretion is thus poured out on to the internal or oral 
surfaces of the labella. Its function is not known, 
6 



42 



MEDICAL ENTOMOLOGY 



The labella are oval lobes, together about the same diameter as the end 

of the labium when in the position of rest, but capable of great disten- 

,^ .... sion and change of form. They are completely sepa- 
The Labella ° , • r i i • i • 

rated from one another m front by a fissure which is 

continuous with the groove on the anterior surface of the labium, and 
which extends a little distance on to the posterior surface also, partially 
separating them on that aspect. Each labellum has an outer and an 
inner wall, which enclose a space continuous with the haematocoele of 
the labium, and therefore with the rest of the body cavity. 

The outer wall is continuous with the outer wall of the labium. It 
consists of membrane, reinforced, especially at the distal border, with a 
deposit of chitin sufficient to impart to it a certain amount of rigidity. It 
bears many long and short hairs scattered over its surface, and a promi- 
nent fringe of macrochaetae at the distal margin of the proboscis. 

The inner walls of the labella in the resting state are in contact with 
one another, but when in use are diverged so as to come into the same 
plane, lying perpendicular to the long axis of the proboscis and in con- 
tact with the surface on which the fly is feeding ; they are very highly 
specialized to form the structure known, from the resemblance of its 
channels to the tracheae or air tubes of the body, as the pseiidotra- 
cheal membrane. This important structure, by means of which the fl}' 
absorbs its food, requires a detailed description. 

The groundwork of the inner wall consists of a thin, transparent, 
and apparently structureless membrane, which is continuous at the dis- 
tal margin of the proboscis with the outer wall of 

''*M"embra^^^ labella, and is attached internally to the discal 

sclerite, a ring of chitin which surrounds the presto- 
mum. This membrane is traversed by a number of grooves, which 
commence at the periphery and converge to the prestomum in a 
regular manner, the upper ones running inwards and downwards, and 
the lower ones inwards and upwards. The details of their arrange- 
ment differ a good deal in even closely allied species. Usually there 
are between twenty and thirty grooves altogether, and of these the distal 
six and the proximal six each unite to form a larger channel, which 
opens at the prestomum, while the middle channels open directly. Those 
formed by the union of several separate channels are of a slightly 
different nature to the rest, and are termed collecting channels. 

The minute structure of these channels is very remarkable. Each 
is an actual depression in the homogenous membrane which forms the 
inner wall of the labellum. The lumen of the groove, which in section 



PSEUDOTRACHEAL MEMBRANE OF MUSCA 43 



is shaped like a squat flask with a short neck, is kept open by a series 
of transversely arranged bars of chitin bent to the form of an incom- 
plete loop, the shape of the channel (Plate VIII, figs. 2 and 3). Each 
of these incomplete rings is bifid at one end and simply expanded at 
the other ; they are set closely side by side throughout the length of 
the channel, and each ring is placed in the reverse direction to those 
on either side of it. There is, therefore, a series of alternate bifid ends 
and expanded ends on each side of the channel (Plate VIII, fig. 4), and 
over each the membrane is tightly tacked down. When the labella 
are in use the two ends of each ring are approximated to one another, 
and there is little if any space between them through which the fluid 
could pass ; the actual openings into the lumen are the shallow grooves 
between the bifid ends of the rings, at right angles to the long axis of 
the channel. 

Graham-Smith, from whose recent paper many of the above details 
are taken, terms the space between the arms of the fork the ' inter- 
bifid space ', and the groove which leads through it to the lumen of 
the channel the ' interbifid ' groove. Now it is evident that, if this be 
the normal path up which the fluid is sucked, the size of the groove 
or space will limit the size of the particles which the fly can ingest, 
a somewhat important point with regard to its disease carrying powers. 
Graham-Smith gives the following measurements for some parts of the 
system: — 



pseudotracheae 
Diameter at 



Interbifid spaces 

Diameter near the ends 
of the pseudotracheae 



Calliphora erythrocephala 
Sarcophaga carnaria 
Lucilia caesar 

Faniiia (Homolomyia) canicularis 
Ophyra anthrax 
Musca domestica 



Proximal end 


Distal end 


Proximal 


Distal 


02 


01 


•006 


"004 mm. 


•02 


01 


005 


•004 mm. 


02 


01 


•006 


•004 mm. 


•016 


•008 


•006 


004 mm. 


016 


•008 


•006 


004 mm. 


016 


008 


004 


•003 mm. 



The method by which the pseudotracheal channels terminate at the 
prestomum differs a good deal in different species. In some the rings 
become increased in depth, and arranged obliquely instead of perpendic- 
ular to the surface, and then split in the middle line, the lateral halves 
separating and coming to lie one in advance of the other. The terminal 
portions are larger and longer than the rest, and become attached either 
to the discal sclerite or to the membrane immediately distal to it. In 



44 



MEDICAL ENTOMOLOGY 



other cases the rings develop a median prominence, directed proximally, 
and so appear T-shaped. The most proximal of these modified rings is 
then attached to the prestomum. 

At the margin of the prestomum, between the terminations of 
the pseudotracheae, there is a series of minute tooth-like processes, 

which, though of little importance in the economy of 
Teeth*""*' Mtisca, are of great interest as being the homologues 

of the powerful biting teeth of the blood-sucking 
forms. They differ in number and arrangement in closely allied 
species, but preserve a general similarity. Each tooth is an elongate slip 
of thin chitin, broader at the distal end than proximally, and with 
a finely serrated but extremely thin margin. The lateral borders are 
thickened into rods, which articulate with the edge of the discal 
sclerite. In Miisca doinestica (Plate IX, fig. 5) there are three such 
rows of teeth, the lateral borders of those of the two distal rows separat- 
ing from one another and gaining attachment to the membrane between 
the terminations of the pseudotracheae, while those of the proximal row 
articulate with the sclerite. There are usually four to six teeth in each 
row, at each side. 

The articulation between the labium and the labella is divided into 
two joints, one anterior and the other posterior. Their importance from 
our present point of view is that they are the homo- 

*7he'Labe'lla°*' logues of the joints on which the biting apparatus of 
the blood-sucking forms acts. 

The anterior joint is formed by the articulation of the discal sclerite 
with the rods which form the anterior boundary of the labial gutter. 
The discal sclerite of Miisca is a strong loop of chitin, roughly resembling 
a racket in shape. The rounded distal portion forms the boundary 
of the prestomum, and has attached to it the inner walls of the labella, 
or the pseudotracheal membrane, and the prestomal teeth. The portion 
corresponding to the handle of the racket consists of two stout rods, 
of about the same length as the looped portion ; these lie in almost 
the same plane as the loop, and diverge from one another as they 
pass backwards. The sclerite is attached to the lateral rods of the 
labial gutter by short tendons which pass between the distal ends of the 
latter and the posterior surface of the sclerite, at the junction of the 
looped portion and the parallel rods (Plate IX, fig. 8). 

The posterior joint lies between the distal end of the mentum 
and a horse-shoe shaped arch of chitin termed the fitrca (Plate IX, fig. 4). 
The distal end of the mentum is somewhat contracted, and has in 



PLATE IX 



Figure 1. 

Figure 2. 



Figure 3. 



Figure 4. 



Figure 5. 



Figure 6. 



Figure 7. 



Figure 8. 



Tlie labrum-epipharynx of Musca iiebitlo. 

The prestomal teeth and terminations of pseudotracheal 

channels of Musca convexifroits, Thomson, ch.r., 

the chitinous strands which surround and support the 

pseudotracheae at their insertions, and are evidently 

homologous with tlie teeth, x 450. 

Two of the prestomal teeth of Musca pattoni, a species 

allied to the last, and of like habit. Note the 

difference in the method of termination of the rings of 

the pseudotrachea. x 600. 

The mentum of Musca nebulo, m., showing the two 
divisions of the fork, f. and f'., separated by the incision, 
i., and supporting the furca, from the median portion of 
which there is a projection, this being closely fused, 
like the rest of the furca, with the external wall of the 
labella. x 100. 

A part of the inner wall of the labella of Musca 
doniestica, showing the three rows of teeth, t., t'., and 
t"., and the terminations of the pseudotracheae. In all 
species of Musca examined only the distal portion of 
the tooth is free from the membrane. x\fter Krjepelin. 
The discal sclerite of PhiJaeinatomyia insignis, 
attached to the thickened lateral rods, l.r., which form 
the margins of the labial gutter. The teeth, as 
shown in figure 8 on the last plate, are attached by 
membrane, not by rigid chitin, to the concave distal 
margin, x 250. 

The proboscis of Pliilaeiiiatoniyia gunici, photo- 
graphed from a cleared preparation. The labrum-epi- 
pharynx, hypopharynx, and labial gutter are placed in 
order to the left of the palps. The discal sclerite with 
the attached teeth is dissected from its attachment to 
the labial gutter, the labellar v/all having been ruptur- 
ed. Microphotograph by Major Kirkpatrick, I. M. S. 
X30. 

The anterior wall of the haustellum of Musca nebulo, 
with the discal sclerite attached. The hypopharynx is 
partially fused with the thin labial gutter. Note the 
lateral rods, attached to the discal sclerite- in front and 
fused with the membraneous wall behind. The mem- 
brane, m., connects the mentum and the labial gutter. 




44 



PROBOSCIS OF MUSCA: MOVEMENTS 4:3 



its margin a square-shaped incision. At each side of this there is a stout 
chitinous rod, those of the two sides diverging from one another 
as they pass downwards ; the rods have a thinner portion about 
the middle of their length, so that one may speak of the two halves 
as the proximal and distal portions of the fork of the mentum. The 
furca lies between the arms of the fork. It is a thickening of the wall 
of the labella, and is at every point closely attached to the membraneous 
wall in this region, so that the labella must always follow it in its move- 
ments. 

The movements of the proboscis are best discussed together with 

the musculature (Plate VIII, fig. 1), taking each joint in turn. It has 

already been stated that the proboscis is completely 

retractile, a fact which will be familiar to all who have Movements of 

the Proboscis 

watched the movements of the common house fly. 

The mechanism of extension and retraction will be described first. 

Extension of the rostrum on the head is brought about by the rotation 
of the fulcrum downwards and forwards on the fixed point provided by 
the attachment of the anterior arch to the epicranial wall. This is 
brought about, not by direct muscular action, but by the distension of 
the two large lateral air sacs which are contained within the wall of the 
rostrum, behind the fulcrum. If one may use the simile, the rostrum is 
thrust out and straightened as one might extend the finger of a glove by 
blowing into it. The motive force is provided by the muscles which act 
in respiration. 

Extension of the haustellum on the rostrum is brought about by the 
contraction of a pair of muscles which arise from the lower end of the 
fulcrum and are inserted into the expanded upper ends of the labral 
apodemes. In the resting position the apodemes diverge like the arms 
of a V, while in the extended position they are almost parallel to 
one another. As the origin and insertion of the muscles are approxi- 
mated the labrum-epipharynx, and with it the labium, is straightened 
on the rostrum ; an instance, as Kraepelin remarked, of the application 
of the parallelogram of forces. 

Retraction of the rostrum within the head cavity is brought about by 
two pairs of muscles, a short pair running between the posterior cornua 
of the fulcrum and the internal surface of the wall of the head capsule 
below the antennae, and a long pair passing between the upper end of 
the mentum and the region of the occipital foramen. The two pairs 
acting together rotate the fulcrum in a backward and upward direction, 
and at the same time pull it within the head. 



46 



MEDICAL ENTOMOLOGY 



Retraction of the haustellum, or rather flexion of it on the rostrum, 
is accompHshed mainly by a pair of muscles which pass between the 
anterior arch and the distal ends of the labral apodemes, and act in 
opposition to the extensors of the haustellum. 

In addition to these main muscle bundles there are many more, on 
both the anterior and posterior sides of the fulcrum, the functions of 
which are difficult to determine on account of their small si^e. Their 
distribution and attachments are described in Kraepelin's paper on 
Miisca doinestica, and in Hansen's account of Stomoxys. 

In the labium there are three pairs of muscles, two of which act 
upon the joints between it and the labella. (Plate VIII, fig. 1, and 
Plate X, fig. 2.) The first of these is situated in front of and be- 
tween the other pair, and runs from the upper end of the mentum, 
and from the posterior surface of the upper end of the labial gutter, 
to the posterior rods of the discal sclerite. The second, situated 
behind and rather external to these, is inserted into the lateral arms 
of the furca. These two pairs of muscles, which are not very clearly 
differentiated from one another in sections, have a double function. 
When they contract together the result is that the external wall of the 
labella is rendered taut, and, through their continuity, the internal wall 
also ; further contraction would result in withdrawing the pseudotracheal 
membrane and exposing the prestomal teeth. When the anterior mus- 
cles alone contract, the discal sclerite is rotated until it becomes per- 
pendicular to the labium. When the posterior pair contracts the exter- 
nal wall of the labella is withdrawn, and the pseudotracheal membrane 
exposed. Owing to the lax nature of the wall of the labium, contrac- 
tion of both muscles will also reduce its long diameter and increase 
its transverse one. 

The third muscle is transverse in direction, and runs between the 
labial gutter and the mentum in the lower part of the labium. It 
will, therefore, counteract the last mentioned action of the two longi- 
.tudinal muscles. 

The movements of the labella are somewhat complex. In the 
resting position the space between the two walls is practically non- 
existent ; the pseudotracheal membranes of the two 

Movements of the c,[des are in contact with one another, and the free ends 
Labella ^ • • 

of the discal sclerite are directed forwards, the labella 

lying slightly behind the end of the haustellum, while the latter is folded 
against the retracted rostrum. When they are in use, however, the 
space between the inner and outer walls of each labellum is distended 



PROBOSCIS IN THE BLOOD-SUCKING MUSCIDAE 47 



with the blood of the insect, forced down from the haustellum and the 
rostrum by respiratory movements, aided probably by the transverse 
muscle at the lower end of the labium. The discal sclerite is rotated 
by the anterior set of muscles until the prestomum which it surrounds 
is parallel with the food surface. The furca is pulled upwards by the 
posterior muscles, and, as the external walls are pulled out of the way, 
the internal walls are pulled apart and into a plane perpendicular to that 
which they occupy in the resting position, until they are parallel with the 
food surface. When in this position the oral surface of the labella forms 
a pad, which, by virtue of its fluid contents, is easily applied to even an 
irregular surface. The fluid can then be sucked through the interbifid 
grooves and up the food canal, by the muscles of the pharynx. 

That the oral lobes are really distended with blood can be easily demon- 
strated by laying an etherized fly on a slide, and compressing the head 
gently, without using sufficient force to rupture the contents. First, 
owing to the pressure driving the air out of the air sacs in the 
head into those in the rostrum, the latter is extended. Then, on 
continuing the pressure, the oral lobes are distended, and the pseudo- 
tracheal membrane exposed. Sometimes a small trachea ruptures in 
the manoeuvre, and a minute air bubble can be seen to float to the 
uppermost surface. If the pseudotracheal membrane is punctured with 
a fine needle while it is distended a drop of a rather viscid yellowish 
fluid exudes. This is the blood of the fly. 

The key to the structure and mechanism of the proboscis in the 
blood-sucking Muscidae lies in the recognition of the homology of the 
parts with those of the non-biting forms, such as Musca. 
The cutting organs by which the wound is made are Mlscidae"*'"^ 
the teeth, which are highly elaborated forms of the 
prestomal teeth as seen in Musca. 

Before going into the details of structure it will be of advantage 
to discuss for a moment the directions in which change is to be looked 
for in the adaptation of the Muscid proboscis to the blood-sucking habit. 
The first essential is a cutting apparatus, and it is found, therefore, that 
the teeth become increased in size and strength even in the earliest 
stages of the evolution. This necessitates increased strength in the 
structures which support them, and in the muscles and joints through 
which they come into play. Both the anterior and posterior joints there- 
fore become consolidated, and the discal sclerite undergoes early and 
marked changes. In the second place, a long and narrow proboscis, ter- 
minating in a point, is essential if it is actually to pierce the skin, and 



48 



MEDICAL ENTOMOLOGY 



in the higher forms the labella are, therefore, reduced in size, the pseudo- 
tracheal membrane, no longer required for the absorption of food, disap- 
pears, and the labium becomes narrowed in its distal part. The muscles, 
more powerful than those of Miisca, are displaced backwards, and are 
contained in a dilated portion of the labium known as the bulb. To 
ensure, rigidity the labium, which now becomes a piercing stj'let, is 
greatly consolidated, the mentum extends further around the surface, 
and the labial gutter becomes very much thicker. In the higher forms 
the posterior joint, by means of which the external labellar wall is drawn 
backwards and the teeth everted, becomes a very important part of the 
apparatus. At the same time the joints between the haustellum and 
the rostrum, and between the latter and the head, remain little altered, 
and although on account of its increased length the haustellum can no 
longer be concealed when it is retracted, it is held in the same position 
as that of Miisca, both in use and in repose. In the higher forms the 
tip of the haustellum projects conspicuously in front of the head when 
at rest. 

The three species of the genus Pliilaematomyia at present known show 
separate and early stages of specialization. In all the outward form 
of the proboscis, as well as that of the fly, is identical 
The Genus Philae- ^^.j^^ ^j^^^^ except in minor points only found 

matomyia . . . 

by a careful comparison. The proboscis is completely 

retractile, and possesses a complete and presumably functional pseudo- 
tracheal membrane. 

In Philaematoinyia lineata, Brunetti, the teeth are easily recognized 
as the homologues of the prestomal teeth of Miisca. There are four 
on each side, each shaped like a rose thorn, attached to the membrane 
between the terminations of the pseudotracheae by expanded bases, and 
to the edge of the discal sclerite by their rather elongated distal ends. 
Like those in Miisca, they show evidence of being composed of two 
lateral portions. The pseudotracheal membrane shows no change except 
in the smaller number of channels. The discal sclerite is broadened 
out distally, so that it becomes more V-shaped, and is much stronger. 
The hypopharynx, which closely resembles that of Miisca, is separated 
completely from the labial gutter, a condition always found in true blood- 
sucking flies. 

The most important advance in structure in this fly is the separa- 
tion of the discal sclerite (Plate XII, fig. 2) into two parts, a condition 
which is found to a much more marked degree in all the other more 
specialized forms. In lineata all that can be seen is an oblique fissure 



PROBOSCIS OF PHILAEMATOMYIA 



49 



running from the internal border of the looped portion of the sclerite, 
at the junction of the distal and middle thirds, to the posterior end. 
The sclerite is thus separated into a distal part, which may at once 
be termed the axial apophysis, including the apex of the sclerite and 
a small portion of each lateral side ; and a proximal portion, including 
that part which bears the teeth and the rods to which the muscles are 
attached. The posterior elongated portions may be termed the lahellar 
rods, and the raised flange which bears the teeth the tooth plate. The 
importance of these distinctions will be seen presently. 

The next species, Philaematomyia gtirnei, Patton and Cragg, 
(Plate IX, fig. 7) has six well developed teeth and two smaller ones on each 
side. Each tooth (Plate VIII, fig. 5) has the same general shape as those 
of the last species, but is thicker, more deeply pigmented, shorter, and has 
a more expanded base. The bases of the teeth are not united directly 
to the discal sclerite, but are attached to the membrane by their bases. 
They are pressed more closely together, their proximal limits forming a 
curved line which corresponds to that of the tooth plate ; the teeth on each 
side, in fact, fit into the cup-shaped depression in the side of the sclerite. 

The discal sclerite is a thick and heavily pigmented structure, in which 
two parts are clearly differentiated ; the axial apophysis is a stout conical 
piece, the distal end of which is free ; the labellar rods are very strong, 
and are wedge-shaped, the broad ends of the wedges being directed dis- 
tally, and attached by their internal borders to the axial apophysis. The 
apophysis thus comes to lie between the two labellar rods, its distal point 
being on about the same level as the termination of the tooth plate. 

The labial gutter in this fly is a thick and densely pigmented structure, 
which must materially assist in keeping the proboscis rigid under strain. 
Its articulation with the sclerite, which is placed in a position exactly 
corresponding with that of Musca, is much more defined. On the 
upper two-thirds of the posterior surface of the gutter there is a median 
backward projection, extending into the cavity of the labium and divid- 
ing the latter into two halves. This is the 'keel' of the labial gutter, 
and is developed mainly to provide attachment for the muscles which act 
upon the anterior joint. 

The method of termination of the pseudotracheal channels in this 
species should be particularly noted, for it furnishes the explanation of 
much more complex structures in the higher forms. The rings become 
elongated near the border of the sclerite, and divide in the middle line, 
the parts being of unequal length and placed one in advance of the other. 
As the sclerite is approached, the segments become longer and more 
7 



50 



MEDICAL ENTOMOLOGY 



separated from one another, and are also broadened out. The last pair, 
which are situated opposite one another, are enlarged into broad leaf-like 
blades, set one on each side of the termination of the channel. 

Philaematomyia insignis, Austen (Plate X, fig. 1), represents a much 
more advanced condition, although the outward form of the proboscis 
- - remains practically the same. There are four teeth 

'"'"'hirgnis"*'* each side (Plate VIII, fig. 8), of the same shape 

as those of giirnei, but larger and stouter, and more 
closely approximated at their bases. The two middle teeth are rather 
larger than the lateral ones, but on account of the curvature of the 
recess into which they fit the apices of all are on the same level. 

Between the teeth there is a well-developed and complex interdental 
armature. This consists of two sets of processes between each two 
adjacent teeth. Each set consists of five or six small leaf-like blades 
with deeply serrated edges, arising from a common stalk at different 
levels and partly superimposed upon one another. The two sets of 
each pair diverge distallj' so as to enclose the termination of one of the 
pseudotracheal channels. 

The discal sclerite (Plate IX, fig. 6) in this species is very much 
modified from that of Musca, and one would hardly be able to recognize 
in them the same structure were it not for the intermediate forms. The 
two parts are quite distinct. The labellar rods are stout pigmented 
bars of chitin, flattened from side to side, and almost parallel to one 
another, but diverging a little posteriorly. About the middle point of 
each there is a prominent tubercle on the ventral surface ; the tubercles 
of the two sides articulate with the end of the labial gutter, which is 
moulded to fit them. At the distal end the rods are dilated to form 
shallow receptacles, in which the bases of the teeth rest (Plate VIII, 
fig. 8). The axial apophysis is a thick shield-shaped piece of chitin, 
situated between and behind the labellar rods, binding them firmly to- 
gether. 

The other structures are correspondingly increased in strength. The 
labial gutter (Plate X, figs. 1 and 2) is thicker than in the last species, 
and its articulation with the discal sclerite is more definite. The 
posterior joint, between the fork of the mentum and the furca, is stronger, 
and the furca itself thicker and rounder than in Musca. 

The mechanism of the proboscis in these flies appears to be as follows. 
The rostrum and the haustellum are extended exactly as in Musca. The 
labella are erected by the contraction of the anterior set of muscles 
attached to the proximal ends of the labellar rods, until, in the case at 



PLATE k 



Figure 1. The proboscis oi Philaeiuatoinyia insignis, dra.^vn frotii 
a cleared preparation. Compare with figure 1, Plate 
VIII, noting the increase in proportionate length of 
the haustellum, and the increase in the area of its wall 
which is chitinized. The simile mentioned on page 39 
is realized by imagining that the foot is inserted from 
left to right between the two posterior cornua, 
p.c. X 66. 

Figure 2. A section through the lower part of the haustellum of 
Philaematomyia insignis. ha., haematocoelic space. 
The tracheae, not shown in the drawing, are very small 
at this level, l.sl.g., labial salivary gland, similar to 
that of Miisca. x 650. 

Figure 3. A section through the lower end of the proboscis 
of Lyperosia niiniita. x 755. 

Figure 4. A section through the rostrum of Philaematomyia 
insignis, showing the pharynx and its muscles. The 
tracheal sacs are contracted as a result of shrinkage in 
fixation, a.w., the anterior wall of the rostrum, here 
composed of membrane. The section is below the 
level of the anterior arch of the fulcrum, to which this 
membrane is attached, x 650. 



PROBOSCIS IN STOMOXYDINAE 



51 



least of insignis, the rods are almost in line with the labial gutter. The 
posterior set of muscles then contracts, and draws the furca upwards, the 
latter carrying with it the external wall, and through their continuity 
the internal wall also, till the teeth are rotated outwards on their 
bases. This turns their cutting edges outwards, and draws them through 
the wound, and is the essential feature of the cutting act. It is possible 
that the teeth are also used in a scraping manner, by alternating contrac- 
tions and relaxations of the anterior set of muscles, the teeth being held 
in the everted position by the action of the posterior set. The length of 
the lever to the end of which the teeth are attached would make this 
action more effective in insignis than in any of the others. Whether 
the pseudotracheal membrane is used in the same way as that of Musca 
it is difficult to say, but it appears probable. The proboscis in this 
genus is not a piercing organ, and, although the cutting apparatus is an 
extremely efficient one, the wound made must be a scarification rather 
than a puncture. Probably the fly bores its way down to the level of 
the blood by rapidly repeated eversions of the teeth, and by using the 
everted teeth as a scraper, the discal sclerite being moved up and down 
on its articulation with the labial gutter; the blood having been reached, 
it is sucked up through the pseudotracheal channels exactly as is done 
by Musca. 

The first two species described are comparatively rare flies and have 
no special interest apart from their anatomy. The third is common and 
widely distributed. It is highly probable that if a systematic examina- 
tion of the proboscides of muscid flies known to be blood-feeders but 
having a retractile proboscis were made, many more species would be 
found. 

In the next group of flies, of which Stonioxys is the best known ex- 
ample, there is a definite advance in the adaptation of the proboscis to 

the blood-sucking habit. The proboscis is a true pierc- 

, . ... , . , , • The Stomoxydinae 

mg organ, and is actually mserted mto the skm. 

The most obvious change, one so marked as to obscure the essential 
similarity, is the elongation of the haustellum. On account of its in- 
creased length it can no longer be concealed when it is retracted, and 
forms a conspicuous projection in front of the head when the fly is at 
rest. The rostrum, on the other hand, is reduced in size. 

In the rostrum, in addition to the smaller size and more compact 

nature of the part, there is an important modification of the buccal cavity. 

This has no resemblance to the buccal cavity of Musca 

1 r 1 ^ 1 in- . / , The buccal cavity 

or to that of the Orthorraphic flies, but has become 



52 



MEDICAL ENTOMOLOGY 



altered to form a duct with a wide lumen, connecting the lower end 
of the pharynx with the food canal in the haustellum. The wall of this 
duct, which is of uniform calibre throughout, is composed of two layers 
(Plate XII, fig. 4). The internal one is membraneous in the lower 
part, and composed of thin chitin in the portion lying between the two 
sides of the fulcrum, which are produced downwards in a funnel-shaped 
manner. The outer layer is composed of a series of thick chitinous rings 
set side by side in the same manner as those of a pseudotracheal channel. 
The rings are open in front, and much thicker posteriorly than at the 
sides, approaching one another so closely that when seen from the side 
they appear as if united in the middle line. Such a channel can be 
bent without its lumen becoming occluded, and will not collapse when 
the pressure within it is reduced during the sucking action.* In the 
resting position the rostrum and haustellum are in the same relation to 
one another as is the case in Musca, and the buccal cavity is acutely 
flexed (Plate XI, fig. 1). 

The labium is almost entirely chitinous, the membrane in its wall be- 
ing confined to a narrow strip which connects the mentum and the labial 
gutter (Plate X, fig. 3). The mentum is spindle-shaped, narrow in 
its distal part and expanded at the upper end into the 'bulb', in which 
the muscles are contained; it extends throughout the sides as well as the 
posterior surface, leaving only a narrow interval in front. The degree to 
which the mentum is narrowed distally and expanded above differs in 
the different genera, and is a good index of the degree of specialization. 
The labial gutter is not so conspicuous in these forms as it is in Philae- 
matomyia, for its place in supporting the biting apparatus is to a great 
extent taken by the mentum. It is, however, thick and strong in the 
lower part of the haustellum, in the region of the anterior joint. The 
'keel' is not so well developed, and is restricted to the lower half or 
third of the gutter, this being due to the fact that the anterior joint does 
not play such an important part in the mechanism, and that con- 
sequently its muscles are not so well developed (Plate X, fig. 3). 

The labella are small oval lobes, which, when the proboscis is 
in the position of rest, are little if at all broader than the end of the 

labium. Each is composed, as in Musca, of an inner 
The Labella in the outer wall enclosing a space which is a part 

Stomoxydinae , , , , ^, • . 

of the haematocoele. The outer wall is contmuous 

with the wall of the haustellum and is composed of membrane, in 

*A ringed wall of a similar nature is commonly found in the salivary duct, where it has 
to resist the action of the salivary pump. 



BITING APPARATUS: STOMOXYDINAE 53 



which there are developed plates of thin chitin, the extent of the chiti- 
nization and the distribution of the plates differing in the different 
genera. At the distal margin, where the two walls are continuous, 
there is a fringe of more or less conspicuous macrochaetae. The inner 
wall is of about equal extent, and there is in no case a definite pseudo- 
tracheal membrane, though in Haeinatobia and Bdellolarynx there 
are well marked traces of it ; it is composed of a strong but homoge- 
nous sheet of tissue, attached internally to the discal sclerite, and 
continuous with the external wall at the distal margin of the 
proboscis. The two inner walls of the labella are in contact with one 
another in the position of rest, the fissure between them being continuous 
with the groove on the anterior surface of the labium, and extending 
for some distance on the posterior surface. 

The teeth and the interdental armature (Plate XII, fig. 5) are situated 
at the proximal limit of the inner surface. The teeth are oblong struct- 
ures of considerable size, three to four times as long as broad, pointed at 
the distal end, and with in most cases a secondary cutting point, 
produced by a deep indentation of the margin of one side. They are 
from four to six in number, and are firmly united to one another by their 
bases, the whole set uniting together proximally to form a thick ridge of 
chitin, the proximal outline of which is curved to correspond with the 
distal margin of the discal sclerite. The teeth are attached to the 
margin of the sclerite by a strong band of fibrous tissue, which is con- 
spicuous in sections on account of its peculiar staining properties. 
The interdental armature consists of one or more rows of leaf-like 
blades, arising from slender stalks, which are attached to the membrane 
of the inner wall between the teeth. The arrangement of the armature 
differs in the different genera, but all conform to the same general type. 
In Stomoxys there is a pair of sets of blades, each consisting of four to 
six, between each pair of teeth, the two sets of each pair diverging from 
one another as in Philaematomyia. In Lyperosia there are two rows 
of blades, a proximal and a distal, of which the latter are the larger. 
The blades are extremely thin, and have a finely granular surface. 

In addition to the blades, there are on the inner wall certain special 
structures which probably have a sensory function. The most con- 
spicuous of these are the ' rod-like hairs ' first described by Stephens 
and Newstead in Stomoxys. These are short but stout and heavily 
pigmented, and are situated opposite the apices of the teeth, usually two 
to each largeltooth. They appear to be grooved on one side, though 
this may be due to the presence of a central channel. 



54 



MEDICAL ENTOMOLOGY 



The articulations between the labium and the labella are strong and 
well defined. The anterior articulation, between the discal sclerite and 
the labial gutter, is a close one, and permits of only a very limited range 
of movement, while the posterior one permits of a wider, though much 
more defined, excursion than that of Musca or Philaematoinyia . 

The discal sderite (Plate XII, fig. 3 and Plate XIII, fig. 7) is 
completely altered in form from the condition seen in Musca. It now 
forms a collar around the prestomum, articulating with the end of the 
labial gutter behind, and bearing the teeth at the distal end. The parts 
representing the labellar rods and the axial apophysis are well distin- 
guished from one another. The labellar rods are flattened plates, parallel 
with one another, but concave on their opposing surfaces, arranged 
vertically in the long axis of the proboscis, and narrower at the proximal 
end than distally. The distal margins are concave, to correspond with 
the curvature of the ridge formed by the united bases of the teeth, to 
which they are attached on each side by a strong band of fibrous tissue. 
The narrow proximal ends are moulded to fit the end of the labial gut- 
ter ; the dorsal posterior angle of each is hollowed out to an L-shaped 
notch, into which the lateral rod of the gutter, produced distally and 
separated from the median ventral portion, is fitted. The middle portion 
of the gutter is also produced to a blunt point on the ventral aspect, and 
this fits between the two plates of the sclerite, the whole producing an 
articulation which can permit of only a limited amount of movement. 

The axial apophysis is a thick rounded mass of chitin, situated be- 
tween and behind the labellar rods, to which it is closely fused ; it thus 
binds them together and forms the floor of the groove. The dorsal 
side of the groove is open, and is continuous with the groove on the 
dorsal surface of the labium. 

The posterior joint (Plate XII, fig. 1, and Plate XIII, fig. 7), be- 
tween the fork of the mentum and the furca, is the one on which the 
most important muscles of the cutting apparatus act. The parts bear 
little superficial resemblance to those of Philaematoinyia, for they are 
moulded to form a strong and compact joint which is capable of bear- 
ing a considerable strain. The distal end of the mentum is cut away 
obliquely upwards and backwards, so that the posterior surface extends 
considerably beyond the anterior. On the ventral side there are two 
thick wedge-shaped rods, the broad ends of which are directed towards 
the labella ; these are the homologues of the proximal portions of the fork 
of the mentum. The furca is a thick chitinous arch, embracing the 
posterior and lateral aspects of the labella, and so moulded as to 



PLATE.XI. 




t»LATE XI 



Figure 1. The proboscis of Stoiiio.xys calcttraiis. h., the bulb. 

Note the resemblance of the buccal cavity, which in the 
Stomoxydinae is merely a tube up which the food is 
conveyed to the pharynx, to a trachea. In a fresh 
preparation the tracheae can be seen on either side of 
it, expanding above into air sacs, x 36. 

Figure 2. The proboscis of Glossina subiuorsitans. d.a., the 
dark area on the posterior surface of the labella, as 
shown in Plate XIII, figure 8. x 50. 

Figure 3. The proboscis of Hippobosca inacttlata, drawn from 
a cleared preparation dissected out of the head. The 
parts are shown in the position of full extension. In 
the resting position the whole of the piercing part of 
the haustellum is concealed between the palps, while 
the bulb is within the head. Compare with figure 3, 
Plate XIII. X 44. 



MECHANISM OF PROBOSCIS: STOMOXYDINAE 55 



fit closely against the broad ends of the fork. On each side of and 
behind the furca there is a small rod, closely pressed against the 
furca but not fused with it, which represents the distal arm of the 
fork of the mentum, displaced forward and separated from the proxi- 
mal arm. 

It will be noted that there is a triangular space between the lateral 
arm of the furca and the truncated end of the mentum, when the 
proboscis is seen in profile (Plate XIII, fig. 7). This is filled in by 
membrane continuous with the wall of the labellum and with the 
mentum. In cleared preparations the labial gutter, which is thickest at 
this point, can be seen at the dorsal side of the triangle. The membrane 
is strengthened by the presence of numerous small oval plates of chitin, 
and is thrown into several folds. 

The mechanism of the proboscis in the blood-sucking Muscidae is an 
extreniely interesting one, in view of the close similarity with Musca. 
The rostrum and haustellum are extended and retract- 
ed in the manner already described, the only differ- Mechanism of the 

... Proboscis 
ence being that on account of its increased length 

the haustellum remains conspicuous in retraction, projecting in front 
of the head. , When extended for use the rostrum and haustellum, 
as in Musca, are brought into line with one another, the proboscis 
being usually held pointing downwards and a little forwards. The 
cutting apparatus is then brought into action by the posterior set of 
muscles, which are attached to the lateral arms of the furca and to the 
adjacent wall of the labellum. The contraction of these muscles rotates 
the furca on the fixed point provided by the expanded ends of the mental 
forks, and as the lateral arms pass backwards they carry with them, 
because of their close attachments, the external labellar walls. When 
this occurs the internal walls of the labella are pulled upon, and are 
carried backwards as far as their attachment to the discal sclerite will 
permit. As a result of a complete contraction, therefore, the lateral 
arms of the furca are directed upwards and backwards until they make, 
with the ventral border of the mentum, a narrow angle open towards the 
head, the arms themselves lying in the membraneous triangle referred to 
above ; the external wall of the labellum is displaced bodily upwards, 
retaining its relation to the furca ; the internal walls of the labella 
become external, being rotated through half a circle on their attachment 
to the discal sclerite, the distal border of which, that is to say, 
the prestomum, becomes the most distal point of the proboscis. 
As a result of the eversion of the labellar walls, the teeth and the 



56 



MEDICAL ENTOMOLOGY 



interdental armature are rotated outwards and upwards on their 
bases, which are moved with the rest of the internal wall, and as this 
occurs their cutting points are pulled upwards through the wound, cut- 
ting as they go. It is by repeated contractions of these muscles, 
producing eversion of the teeth, that the wound is made. 

In the position of action thus produced (Plate VIII, fig. 7) the 
interdental armature is swept upwards in advance of the teeth, and as 
each contraction occurs the blades sweep the surface of the wound clear. 
When the wound is made, and the fly begins to suck up the blood, they 
surround the prestomum like a hollow brush, and so prevent the ingress 
into the canal of particles too large for its lumen, a function of peculiar 
interest when considered in relation to the homology of the parts, for the 
interdental armature in the Stomoxydinae is developed from the remains 
of the rings of the pseudotracheae as seen in Musca. 

The contractions of the posterior set of muscles are presumably 
repeated with very great rapidity, as is the case in the biting apparatus of 
the Orthorraphic flies, and it is necessary to consider by what mechanism 
the parts can be replaced in position for the next contraction. To 
understand how this occurs one must revert for a moment to the struc- 
ture of the labella. In the resting position the prestomum is at some 
distance from the distal end of the proboscis, being in fact separated 
from it by the total depth of the inner walls. This may be regarded as 
an invagination, the distal borders of the sclerite, which bound the 
prestomum, being the apex. Now when the external wall is displaced 
upwards and the inner wall everted, this invagination is undone, and the 
blood which was between its inner and outer walls is driven up- 
wards. The return of the parts to the resting position is brought about 
by the pressure of blood in the proboscis, in exactly the same way as is 
the case in the distension of the oral lobes of Musca. This is due partly 
to the respiratory movements of the fly, and partly to the contraction of 
the transverse muscles which pass between the mentum and the labial 
gutter, in the lower end of the labium. 

The muscles of the labium are divided into the same bundles as in 
Musca. The posterior set, however, which has to pull the teeth through 
the tissues, and has therefore to act against considerable resistance, is 
very much larger than the others, and occupies practically the whole of 
the bulb. In the narrow part of the proboscis the muscle fibres are 
replaced by tendons, which spread out at their insertions so as to gain 
attachment to the external wall of the labellum, as well as to the furca. 
The anterior set, which in Philaematomyia erects the labellar rods, is 



PROBOSCIS IN THE STOMOXYDINAE 57 



not well developed, for the anterior joint is practically fixed in a position 

of incomplete extension. 

The labrum-epipharynx and the hypopharynx are much more slender 

and narrower than those of Musca, since they are more effectively 

concealed and protected by the deeper labial gutter. 

TV, \ c i A • t A ■ u ^ Labpum-epipharynx 

The canal for the food is formed m the same way, but hypopharynx 

with this notable difference, that in the upper part 

of the haustellum it becomes closed by the fusion of the sides of the 

groove formed by the epipharynx, and the union of the dorsal lamina of 

the hypopharynx with this. The hypopharynx is free from the labial 

gutter except at the upper end. 

Both the labrum-epipharynx and the hypopharynx are shorter than 
the rest of the haustellum, and do not, in the resting position, reach 
beyond the level of the furca. They cannot, therefore, take any part in 
the making of the wound, and have, as one would expect, thin and 
flaccid distal ends. On the ventral surface of the distal end of the 
epipharynx there are several sensory tubercles or hairs, which, as they 
are situated at the opening of the food canal, probably play a part in the 
mechanism by which the size of the opening is regulated. 

The distance between the terminations of the labrum-epipharynx 
and hypopharynx and the margin of the prestomum, as defined by the 
discal sclerite, is materially reduced in the position of action, when 
the wound has been made to a satisfactory depth, by a longitudi- 
nal compression of the mentum. The surface of the latter is marked 
by a series of transverse ridges and furrows, which extend all round the 
organ, and are the most marked in its narrowest part. The deepening 
of the furrows must be accompanied by a decrease in the length of the 
labium. This is brought about by the further contraction of the power- 
ful muscles of the bulb, which press the furca against the fork of the 
mentum, and so compress the latter towards its proximal end. The ridges 
and furrows are always more marked in specimens fixed in the everted 
position than in those in which the labella are closed. 

The tracheal structures in the proboscis are the same as those of 
Musca and Philaematomyia. One interesting point may be noted 
with regard to the nerves. There is one large nerve on each side of 
the cavity of the labium, in close contact with the trachea. At the 
upper end of the haustellum the trachea is very much the larger of 
the two, but as they pass downward it diminishes rapidly in size 
as it gives off branches for the supply of the muscles. The 
nerve becomes only a little smaller, and as it enters the labellum is 
8 



58 



MEDICAL ENTOMOLOGY 



larger than the trachea. The labella, while they require comparatively 
little supply of air, require a rich supply of nerves for their complex 
mechanism. 

The labial salivary gland does not occur in the Stomoxydinae, having 
disappeared with the pseudotracheal membrane. 

It has been stated that in the proboscis of Haematobia there are to 

be found vestiges of a pseudotracheal membrane. In all other respects 

the mouth parts are similar to those of Stomoxys, such 
Haematobia ^.^ ^ . . . , , 

dmerences as there are, as tor mstance a rather less 

marked spindle shape in the labium, and a smaller disproportion 
between the length of the rostrum and haustellum, indicating that 
the fly is not so far advanced in specialization as the rest of 
the group. At the distal end of the labella there are five small 
triangular flaps (Plate XII, fig. 1), each composed of an inner and 
an outer wall, continuous with the walls of the labella, and enclosing 
between them a space which is continuous with the haematocoele. 
The wall consists for the most part of a thin transparent membrane, 
strengthened by small oval chitinous squamae, and resembles that 
found elsewhere in the non-chitinized area of the proboscis in other 
Stomoxydinae. In the middle line of the inner wall, however, these 
squamae are elongated transversely, and arranged in a row so as 
to form a shallow gutter ; as the region of the teeth is approached they 
are gradually replaced by definite pseudotracheal rings, similar to those 
of Musca, except that the channels do not appear to be quite so narrow 
at the neck. Presumably the channels in the flaps and on the inner 
walls of the labella are used in the same way as those of Musca, to suck 
up the blood, when the haematocoele of the labella is distended. A 
similar condition is found in Bdellolarynx. 

The proboscis of Glossina (Plate XI, fig. 2) is modified from the Musca 
type in very much the same manner as that of the Stomoxydinae, but 
the specialization has gone very much further. The homology can, how- 
ever, be followed fairly closely, and the mechanism is practically the 
same. 

The proboscis is held in front of the head when at rest, but is 

concealed by the palps, which extend to its tip. On account of the great 

. elongation of the haustellum, which in this genus is at 

Glossina 

least three and a half times as long as the rostrum, the 
proboscis is very conspicuous even in the resting position. 

The rostrum has the shape of a very short pyramid, and is almost 
entirely occupied by the fulcrum, this being more compact and more 



PLATE XII 



Figure 1. The labella of Haematohia stimulans, drawn from a 
cleared preparation. {[., the flaps, on the internal sur- 
faces of which are to be found the pseudotracheae. 
p.b., the position of the petiolated blades, p.s., the 
position of the pseudotracheae, in the resting condition, 
m.f., the upper division of the fork of the mentum, on 
which rests the furca. m., the mentum. x 150. 

Figure 2. The discal sclerite of Philaematomyia liiieata. t.p., 
the flange which projects from the distal ends of the 
labellar rods, and to which the teeth are attached. 
X 470. 

Figure 3. The discal sclerite and distal end of the labial gutter 
of Stoiitoxys calcitrans. m.g., the median portion of 
the gutter. The commencement of the keel is shown. 
The teeth are attached by a strong but flexible band of 
fibres to the concave distal end of the sclerite. X 450. 

Figure 4. The lower end of the pharynx of Haematobia 
stimulans, seen from behind, to show the nature of the 
wall of the buccal cavity, r., the rings of chitin which 
surround the tube, x 350. 

Figure 5. The teeth and connected structures of Haematobia 
stimulans, detached from the discal sclerite. x 525. 

Figure 6. An isolated tooth, {Haematobia stimulans) to show the 
secondary teeth on its inner surface. These secondary 
teeth become external when the teeth are everted. 




58 



THE PROBOSCIS : GLOSSINA 



59 



evenly chitinized than in the Stomoxydinae. The labral apodemes 
are correspondingly reduced, and are also thinner than those of the 
forms so far dealt with. The buccal cavity is of the same type as that 
of Miisca, and consists of a small chamber, broader than long, and formed 
from a single plate of chitin, the lateral edges of which are turned for- 
wards and connected across the front by tough membrane ; the epi- 
pharjmx and hypopharynx terminate at this point in a manner similar to 
that described for Musca. 

The haustellum appears on external examination to be an exaggeration 
of the form seen in Stomoxys. It consists of two portions, the upper end 
being swollen and bulbous, the distal part narrowed down to a fine 
st\ let ; the relative proportions of these being approximately one to two 
and a half. When examined in sections and in cleared preparations it is 
found that there are many important differences from the proboscis in the 
Stomoxydinae. In the first place, the labella are not nearly so well marked 
off from the labium proper, and are only very slightly thicker than the 
adjacent part of the proboscis ; secondly, the labial gutter, and not the 
mentum, is the main support of the proboscis. 

The labrum-epipharynx lies throughout in close contact with the labial 
gutter, and since it does not, on that account, need to possess much 
rigidity, it is a very delicate organ. The two constituent parts are close- 
ly welded together, with only a small interval between them at the sides, 
and together form a long inverted gutter ; at the distal end, which is 
situated just distal to the junction of the labium with the labella, the 
gutter is very shallow, but further up the lateral portions are produced in 
a circular direction, so that at the upper end the groove is converted to a 
tunnel with only a small gap in its ventral wall. 

The external surfaces are in contact with the labial gutter, and are 
provided with a row of short teeth which interlock with a corresponding 
set on the gutter, the arrangement serving to prevent any displacement 
of the organ from the groove in which it lies. The distal end is flattened 
and soft, and is provided with a number of fine sensory hairs. At the 
proximal end the two parts separate in the usual manner, the labrum be- 
coming continuous with the membraneous anterior wall of the rostrum, 
the epipharynx fusing with the anterior wall of the buccal cavity. 

The hypopharynx is an exceedingly delicate organ, composed of thin 
and semi-membraneous chitin ; it does not assume the flattened form seen 
in the other Diptera, and consists of little more than the wall of the sali- 
vary duct, with some lateral membraneous expansions in the region of the 
bulb. For a considerable part of its extent, according to Stephens and 



60 



MEDICAL ENTOMOLOGY 



Newstead, it is actually connected to the lateral extremities of the 
labrum by a fine membrane, so that the food canal in the haustellum 
becomes a closed tube. The organ lies for the most part of its length in 
a small median recess in the labial gutter. 

The mentum in the bulb presents no special characters, but in the 
narrow part of the proboscis the chitin is very thin and semi-membraneous, 
and bears a number of peculiar spines on the ventral surface, arranged in 
two parallel rows. It is connected to the labial gutter by a narrow 
membrane divided into polygonal areas. The labial gutter is composed 
of thick chitin, and contributes much more to the rigidity of the 
proboscis than the mentum. In the middle of the haustellum it forms 
an almost complete tube, rather broader in the transverse diameter than 
in the vertical, and with a deep and narrow pocket in the middle ventral 
line for the reception of the hypopharynx. The lateral portions are 
thinner and pointed, and overlap the labrum, to which they are connected 
by the row of interlocking teeth mentioned above ; at this level the sides 
of the mentum are also thickened, so that there is very little space left 
between the anterior and posterior walls of the labium. Distally the 
walls of the gutter become thinner, and are directly continuous with 
the inner walls of the labella, no discal sclerite being differentiated in this 
form. At the upper end of the labium the sides of the gutter are more 
widely separated from one another, and the labrum appears on the 
dorsal surface of the proboscis. 

The biting apparatus (Plate XIII, fig. 9) consists of prestomal teeth 
evidently homologous with those of Miisca, and in addition the ' rasps ', 

and certain sharp spines on the outer wall of the 
^'^of^Gklsstna*"^ labellum. The arrangement at the prestomum is 

as follows. On each of the internal labellar walls 
there are two fissures, which divide it into three equal portions, 
dorsal, middle, and ventral. The main part of each division consists 
of a ' rasp ', an oblong plate, longest in the antero-posterior diameter, 
and traversed by about ten ridges running from the dorsal to the 
ventral side ; each of these is in turn being divided into minute ridges 
running in the long axis of the proboscis. At the distal end of each 
rasp there are two large conical teeth, the internal ones of the dorsal and 
ventral sets being larger than the external. These large teeth arise 
from a small chitinous eminence, at the sides of which there are 
two smaller teeth. Between the two larger teeth of each division, 
and also on the dorsal and ventral surfaces of the inner wall, there 
is a set of excessively fine scales, arranged in a fan-shaped manner, 



PROBOSCIS OF GLOSSINA: MECHANISM 61 



which represent the interdental armature. These are termed by Stephens 
and Newstead the ' fans ' . 

The mechanism of the biting apparatus (Plate XIII, fig. 8), is a 
modification of that described in the Stomoxydinae. On account of the 
disappearance of the discal sclerite there is no anterior joint, all the 
movements taking place on the posterior one. The furca is represented 
by a broad but rather thin transverse bar, the lateral arms of which turn 
forwards and upwards on to the sides of the labella, and are there 
received into shallow pits in the external wall. The fork of the mentum 
is represented by a thickening of the chitin immediately posterior to 
the furca, and consists of two lateral rods united by their broad distal 
ends, and so closely opposed to the furca that they appear to form with 
it a T-shaped piece. Both the furca and these forks are simple thicken- 
ings of the chitin, not nearly so well demarcated as the corresponding 
parts in Stomoxys, and not raised above the surface. 

The external walls of the labella are partly membraneous and partly 
chitinous. On the posterior surface there is a circular area, situated 
about midway between the distal end and the furca, in which the wall is 
thickly chitinized and pigmented. This part, referred to by Stephens and 
Newstead as the 'dark area ', is readily recognized under a low magnifica- 
tion. Posterior to this the wall is membraneous as far as the furca. The 
lateral walls are mainly chitinized, and are produced at the posterior ends 
to a sharp angle on each side. Distal to these angles, and considerably 
removed from them in the position of rest, there is a pair of small pits at 
the end of longitudinal thickenings on the lateral wall of the mentum. 

The muscles of the bulb, which cannot readily be separated into 
bundles, terminate in long tendons which traverse the whole of the 
narrow part of the mentum, and are inserted partly into the lateral 
arms of the furca and partly into the thick and pigmented area anterior 
to it. When they contract the furca, which is fitted into a groove on 
the distal end of the fused rods, is rotated in the usual manner, so 
that its lateral arms come to point in the reverse direction, that is, 
towards the base of the proboscis. As the tendons are also inserted into 
the chitinized area distal to the furca, the posterior wall as a whole is 
drawn upwards together with it, so that there is a complete change in 
the relations of the parts. The dark area is approximated to the middle 
portion of the furca, and the posterior angles of the external walls are 
pulled upwards till they fit into the pits on the lateral wall of the men- 
tum. The teeth and rasps are everted and pulled upwards through the 
wound in the usual manner, following the movement of the external wall. 



62 



MEDICAL ENTOMOLOGY 



The proboscis of Glossina is inserted into the skin for a considerable 
depth, and the eversion of the teeth and upward displacement of 
the external wall must be repeated with very great rapidity. Several 
observers have noticed that when the fly commences to feed it produces 
a faint humming sound, due to a rapid vibration of the wings ; this is 
probably due to the extremely rapid respiratory movements by which the 
blood is forced down into the labella, in order to reduce them to the 
resting position in readiness for the next cutting act. 

The attitude of the fly while feeding is rather different to that of 
the Stomoxydinae, for owing to the reduction of the amount of move- 
ment possible between the rostrum and the head, and between the 
rostrum and the haustellum, the fly has to raise itself a little on its hind 
legs in order to adjust the tip of its proboscis to a position suitable 
for feeding. 

Hippobosca and its allies present a curious condition, for while the 
upper part of the proboscis, or rather the sucking apparatus simply, as 
it is never protruded from the head, resembles that 

(Pulte'x?°^g* 3) Mtisca in many respects, the distal part or proboscis 
proper is more like that of Glossina. The Pupipara 
are not descended from a Glossina-Iike form, but from some remote 
ancestor common to it and to Musca. 

In the resting condition the whole of the sucking apparatus, corre- 
sponding to the rostrum of Musca, and also the posterior part of the 
haustellum, are concealed within the head. The distal part of the 
haustellum, which, as in Glossina, forms a narrow piercing stylet, is 
concealed between the palps, which alone are visible without dissection. 
(Plate XIII, fig. 3.) When the mouth parts are required for use the ful- 
crum is rotated in the same manner as in Musca, and by a similar 
mechanism, with the result that the stylet is pushed forward between 
the palps, and the pharynx, buccal cavity, and haustellum brought 
into line with one another. 

The fulcrum and pharynx are of the same type as in Musca, but dif- 
fer in detail. The ventral plate is strongly concave, and terminates 
posteriorly in very small outwardly directed cornua. 

The Sucking appa ^j^^ lateral plates are narrow, and converge towards 
ratus of Hippobosca \ ° . 

one another in a V-shaped manner ; the anterior arch 

is represented only by a short rod of thick chitin which lies between the 
ends of the lateral plates and is directed antero-posteriorly. (Plate XIII, 
fig. 6.) It is fitted into a semicircular notch at the distal end of the plate 
of chitin which separates the eyes. The ventral wall of the pharynx 



PLATE. Xm. 





PLATE XIII 



Figure 1. Cross section of the narrow part of the haustellum of 
Hippobosca maculata. At this level the labrum and 
epipharynx are completely fused. Higher up the two 
separate, td., the tendon of the muscle of the bulb, 
which retracts the labellar wall and everts the teeth. 
X450. 

Figure 2. A section through the lower part of the buccal cavity. 
X 400. 

Figure 3. The proboscis and sucking apparatus of Hippobosca 
maculata in the position of rest, within the head. 
The palps, which conceal the projecting part of the 
haustellum, are not shown. Note the invagination of 
the membrane around the haustellum, to be attached 
to the base of the bulb as in Stoinoxys. a.pt., the 
antennal pit, sunk below the surface of the head. 
X 50. 

Figure 4. Three of the teeth of the serrated ridge on the outer 
wall of the labella. s.r. in next figure. 

Figure 5. The distal end of the proboscis of Hippobosca maculata, 
showing the membraneous interval which permits of the 
eversion of the wall, s.r., the serrated ridge bearing 
the teeth shown in the last figure, x 200. 

Figure Ti. The articulation of the anterior arch of the fulcrum 
with the wall of the head between the antennal pits. 
The distal edge of the wall is notched for the reception 
of the fulcrum. 

Figure 7. The distal end of the proboscis of Lyperosia miniita, 
with a part of the external wall cut away to show the 
teeth. X 700. 

Figure 8. The distal end of the proboscis of Glossina subinorsit- 
ans, seen from the posterior surface, d.a., the dark 
area, an., prominent angles which fit, in eversion, into 
the cup-shaped tubercles on l.r., lateral thickenings in 
the wall of the mentum. x 200. 

Figure 9. The structures on the inner wall of the labellum of 
Glossina submorsitans. rs., the rasps, t., t'., the 
teeth. fn., the ' fans', representing the interdental 
artnature. x 900. 



PROBOSCIS OF HIPPOBOSCA 



63 



is almost entirely composed of a thick membrane, there being only a 
small elongate area in the middle line which is strongly chitinized ; 
the main mass of the dilator muscles of the pharynx are inserted into 
this median area. 

The buccal cavity in this form has the shape of a long chitinous 
tube, which connects the pharynx with the food canal in the haustel- 
lum. The lateral walls of the tube are much thicker than the dorsal 
and ventral walls, and project outwards and backwards in the distal 
portion of the tube so as to form a shallow groove for the reception 
of the salivary duct. The lumen of the tube is of uniform diameter 
throughout, and is circular, though a little narrower in the dorsal than 
in the ventral half. (Plate XIII, fig. 2.) At the upper end of the buc- 
cal cavity its walls are continuous with those of the pharynx, while 
at the distal end the union with the food canal in the haustellum is 
brought about in a manner similar to that of Miisca ; the cavity is 
slightly dilated, and encloses the end of the food canal, which is here 
a closed tube. The edges are united by a short membrane, so that 
although the continuity of the tube is maintained, free movement is 
possible. 

The haustellum strongly resembles that of Glossina. The bulb oc- 
cupies only the upper third ; the narrow part distal to this is curved 
downwards and forwards, and terminates in a cutting apparatus much 
simpler than that of the Muscidae. The end of the labium is not clearly 
divided into two labella, but the structures which make up the biting 
apparatus are bilaterally arranged. 

The labrum-epipharynx is a relatively strong organ, shaped like a 
long and narrow arrow-head, and rounded on the dorsal surface. (Plate 
XIII, fig. 1.) It is not enclosed by the labial gutter, but forms 
the dorsal aspect of the haustellum, and is beset with two parallel 
rows of minute spines. The labrum and epipharynx are closely fused 
together in the distal part of the proboscis, but separate higher up ; 
the distal end of the labrum is fused with a membrane correspond- 
ing to the anterior surface of the rostrum, \vhile the epipharynx forms a 
closed tube by the union of its sides, and unites with the buccal 
cavity as already described. On the external surface of the sides of 
the labrum there is a row of short spines, where it is pressed against 
the labial gutter. At the distal end the labrum broadens out consider- 
ably, and is produced into two tubercles, which are fitted into corre- 
sponding shallow pits on the distal ends of the labral apodemes, this 
being the reverse of the method of union in the Muscidae, The 



64 



MEDICAL ENTOMOLOGY 



apodemes are long and stout, and terminate at the proximal end in 
rounded points. 

The hypopharynx is a very slender flattened organ, of the type seen 
in the Stomoxydinae, and contains the salivary duct between its two 
layers. At the upper end of the haustellum the flattened lateral areas 
are absorbed ; the dorsal lamina fuses with the closed part of the 
epipharynx, the ventral with the labial gutter, while the salivary duct 
passes into a deep pocket-like recess in the middle of the latter. 

The wall of the labium is composed of the mentum and the labial 
gutter, which serve about equally in rendering the proboscis a rigid 
piercing organ. The mentum in the bulb is composed of rather thin 
chitin, and is devoid of hairs. In the narrow part it is very thick 
and strong, and forms a shallow trough occupied mainly by a 
pair of tendons and some muscle fibres connecting it with the gutter. 
On its external surface there are two parallel rows of minute spines 
extending from the labellar area to the bulb ; the hairs are arranged in 
pairs, the intervals between which diminish progressively as the bulb is 
approached. The labial gutter is a shallow trough of thick chitin, of 
almost as great a breadth as the mentum, to which it is connected by a 
narrow band of thick fibrous tissue. At the sides there is a ridge of chi- 
tin projecting downwards and slightly outwards, in line with the 
lateral margins, so as to give the gutter on section the appearance of 
a letter H, greatly elongated in the transverse diameter. The gutter 
is not depressed between the sides of the mentum, nor does it extend 
sufliciently far forwards to enclose the labrum-epipharynx. It is con- 
tinued unchanged throughout the labellar region, but is slightly dilated at 
the distal end for the reception of the bases of the teeth. 

The cutting apparatus consists of a set of teeth at the prestomum, 
corresponding to the prestomal teeth in the Muscidae, a serrated ridge 
on the external surface of the labellum on each side, 

Brting apparatus ^ modification of the external wall which renders 

of Hippobosca 

the distal portion capable of movement on the rest of 
the mentum. (Plate XIII, fig. 5.) 

There are five prestomal teeth on each side, arranged in a radiate man- 
ner, the middle and largest tooth being directed straight forwards. 
Its distal end is bifid, with two equal arms, while in the teeth on either 
side of it the arm next the middle line is the largest. The proximal ends 
of the teeth are rounded, and are fitted into the dilated end of the labial 
gutter. The external set of teeth (Plate XIII, figs. 4 and 5) are flattened 
and typically serrate, with points directed upwards towards the head. 



PROBOSCIS OF HIPPOBOSCA 



65 



The' distal end of the external wall of the labium is separated from 
the rest by a short interval of thin and flexible membrane, the margin 
proximal to which is a little thickened. The tendons which traverse 
the length of the labium, arising from the muscles of the bulb, are 
inserted into this separated area, so that a contraction of these muscles 
results in drawing the portion of the wall distal to the membrane up- 
wards. This everts the prestomal teeth, and also draws the line of 
teeth on the external surface upwards through the wound, the method of 
action being in all essential points the same as that in Glossina. The 
teeth are thrust back into position for the next cut by the distension of 
the space between the wall in the labellar area and the labial gutter. 
These actions must, of course, be repeated with extreme rapidity. 

The palps are elongate and ovoid in shape, and consist of a single 
joint. Their external surfaces are convex, and are beset with stout hairs, 
while the internal surfaces are flattened. The two are in close contact 
with one another in the position of rest, and are the only part of the 
apparatus which can be seen without dissection. On the inner surface 
of each there is a deep longitudinal gutter, the two gutters forming 
a canal in which the narrow part of the haustellum rests. 

The membrane from which the palps arise is attached above to the 
distal edge of the clypeus, and corresponds to the anterior wall of the 
rostrum. But on account of the position of the haustellum, all of which, 
except that part which lies between the palps, is within the head in 
the position of rest, the membrane, in order to reach its attachment to the 
distal end of the haustellum, has to be invaginated within the head 
around the latter. In sections, therefore, the haustellum appears to be 
surrounded by a tube of membrane, which commences at the aperture 
behind the palps, and terminates by becoming attached to the distal end 
of the bulb. 

The parts corresponding to the rostrum are provided with a muscul- 
ature very closely resembling that of Musca, but having the bundles more 
clearly differentiated from one another than in that form (Plate XIII, fig. 
3). The actions of the muscles are also the same, but the final result, 
instead of being a protrusion of the rostrum from the head and the 
extension of the whole proboscis, is only the protrusion of the haustellum 
from between the palps. The fulcrum is rotated on its attachment to 
the clypeus, so that the pharynx comes into line with the haustellum, 
and at the same time the buccal cavity which connects the two is 
straightened. In the resting position the buccal cavity is bent backwards 
in its lower part, on account of its length. 
9 



66 



MEDICAL ENTOMOLOGY 



The wall of the head capsule is not thrust forward sufficiently in this 
species to justify the term rostrum, but the same sort of movement 
occurs. The invagination of the membrane around the haustellum 
is undone as the piercing stylet is thrust out between the diverging 
palps. (Plate XI, fig. 3.) 

The relations of the muscles are so like those in Miisca that the figure 
will explain itself. 



INTERNAL STRUCTURES OF THE HEAD 

The only internal structures connected with the exo-skeleton of the 
head in the Diptera are the intracranial tunnels and the ptilinum. 
The former occur only in the Orthorraphic flies, while the latter is 
characteristic of the Cyclorrappha. 

The intracranial tunnels (Plate IV, fig. 4) are probably homologous 
with the tentorium of other insects. They occur in all the blood- 
sucking Orthorrapha, and in many of the others. In 
Intracranial Tunnels ° , , ,, , • r i 

most cases they are hollow tunnels, passing from the 

anterior to the posterior wall of the head capsule, and open at each 
end. They are bilateral, those of the two sides converging towards one 
another from behind forwards, on each side of the first part of the suck- 
ing apparatus and a little above it. The posterior opening is situated 
between the base of the proboscis and the occipital foramen, and 
the anterior at the side of the clypeus, below the antennae. The 
tunnel is generally narrowest in its middle position, and in some 
forms, as for instance Simtilium, the lumen is closed at the nar- 
rowest point. 

The function of these tunnels is to support the walls of the head 
cavity, and especially to enable them to resist the action of the powerful 
dilator muscles connected with the sucking apparatus. In Tabaniis they 
are so placed as to transfer the strain of the muscles of the .buccal cavity 
from the anterior to the posterior wall of the head, and, in order to 
distribute the strain over a wider area, the anterior end expands in a 
funnel-shaped manner. The posterior end is attached to a strong bar of 
chitin at the side of the membraneous area of the inferior wall, at the 
base of the proboscis. The fact that they are hollow has no more 
significance than that, weight for weight, a hollow cylinder is stronger 
than a solid rod. 

The submental region, which in the Orthorraphic flies is mostly 
membraneous, is strengthened by the development of strong lateral bars 



THE NECK 



6^ 



of chitin, which are connected posteriorly with the occipital foramen. 

The foramen itself is strengthened and delined above by a thick arch 

of chitin, the extremities of which are turned outwards. The various 

portions of the margins of the foramen have received distinctive names, 

which are of little importance for the present purpose. The rigid 

nature of the margins of the foramen should be remembered when 

dissecting the part. 

The pt Hi nil in is characteristic of the Cyclorrapha, and is related to 

the method by which the imago emerges from the pupal case. The 

external opening, as already described, lies above and ^ ... 

, ■ J r \ -1 The Ptilinum 

at the sides of the antennae, and is known as the 

ptilinal suture. From the margins of this orifice the wall of the head 
cavity is invaginated in the form of a much convoluted membraneous 
sac, the external walls of which are covered with scales of various shapes 
(Plate XVI, fig. 2) ; the internal surface of the membrane has attached to it 
a number of scattered muscle fibres. In sections the sac is found in the 
upper part of the head and in front of the brain; its wall is always 
thrown into very numerous folds, so that on a first examination one 
would hardly recognize it as a sac. In newly-hatched flies it can be 
easily evaginated as a rounded tumour by compressing the head with 
a needle. 

The purpose of the ptilinal sac is to thrust off the end of the puparium 
at the moment the fly is ready to emerge, and this is accomplished 
by the distension of the sac with air, by respiratory movements of 
the body. The method of emergence, and the consequent presence 
of the ptilinal suture in the imago, are two of the essential features 
which separate the Cyclorrapha from the rest of the Diptera ; the 
Orthorrapha do not escape by detaching the end of the pupal case as 
a circular cap, but through a T-shaped opening on the dorsal surface. 
It is this feature which has given the flies the name Cyclorrapha. 

The neck is always well demarcated in the Diptera. In most flies it is 
a simple membraneous tube connecting the head with the thorax, but in 
some Orthorraphic flies the membrane may be strength- 
ened by small lateral plates of chitin. These, how- 
ever, are never sufficiently well developed either to impart any rigidity 
to the neck, such as would enable the fly to use the muscular force of 
the body to thrust its mouth parts into a resistant layer, or to interfere 
with the free movements of the neck. The movements of the neck are 
not extensive, and are limited to the adaptation of the proboscis to 
the position requisite for feeding. They are brought about by certain 



68 



MEDICAL ENTOMOLOGY 



ill-defined bundles of muscles running between the internal surface of 
the neck and the prothorax. 

The structures which pass through the neck are numerous, and some 
knowledge of the anatomy of this region is of importance in dissection. 
When the head is separated from the body by traction these structures 
are exposed, and with care they can be separated from one another, and 
those not required cut off. In the first place, there are always two compara- 
tively large tracheae, one on each side, passing from the thoracic spiracles 
to supply the head with air. On the inner side of these there is a pair of 
salivary ducts or the commencement of the glands. In the middle line 
there are, from the dorsal to the ventral side in order, a minute blood 
vessel, a prolongation of the dorsal heart, so small as to be only seen in 
the larger flies ; the duct of the crop or oesophageal diverticulum,* and be- 
low it the oesophagus ; and below this the nerve cord which connects the 
brain with the thoracic ganglia. A little experience with the larger flies 
enables one to distinguish between these by their size and colour, and in 
dissection it is always sound to cut away boldly all that is not required. 

THE THORAX 

The principles of the structure of the walls of the thorax have already 

been explained in the paragraph on the segmentation of the insect body. 

Briefly, the typical thorax should consist of three parts, 
Segmentation , , . , , 

each representmg a segment, and termed the prothorax, 

mesothorax, and metathorax, respectively. The wall of each segment 
should be composed of a tergite or dorsal plate, a sternite or ventral 
plate which may be divided in the middle line, and two lateral or 
pleural plates, the episternum in contact with the sternite and the 
epimeron in contact with the tergite. But in such a highly-specialized 
group as the Diptera one would hardly expect to find a primitive 
arrangement persisting, and the relations of the parts are moreover 
profoundly altered by the great development of one pair of wings, 
especially since the majority of the Diptera are powerful flyers. Indeed, 
this factor, with the consequent necessity for adequate surface for muscle 
origin and insertion, has introduced so much change that it is a matter of 
the utmost difficulty to allocate the various sclerites to their original 
positions. The wings which have persisted are the mesothoracic pair, 
and in consequence the mesothorax has become greatly increased at 
the expense of the segments in front and behind it, until it now occu- 
pies by far the greater portion of the external wall. The prothorax 

* In Musca and its allies the duct of the crop is ventral to the oesophagus. 



PLATE.W. 




69 



PLATE XIV 



Figure 1. The parts of the exoskeleton of Ciilex fatigaiis. The 
dotted areas indicate soft membrane. The area of 
membrane at the wing base is shaded darkly, pg., 
patagia. eps'., episternum of prothorax. sc"., scutum 
of mesothorax. scl'., scuteHum. mtn'"., metanotum 
(post scutellum, see page 74). h., halter, cv. s., 
cervical sclerite. cx'., cx"., cx'"., coxae of the three 
legs, ms"., mesosternum. The prosternum does not 
appear on the lateral wall, ms'"., the metasternum. 
eps'"., the episternum of the metathorax. a.s., 
anterior spiracle, p.s., posterior spiracle. The seg- 
ments of the abdomen are numbered in order. 

Figure 2. The thorax of Tabaniis albimedhis, seen from the 
inner aspect after dissection, pn'., pronotum. psc"., 
prescutum. t'., tergite of the first segment of the 
abdomen. s'., its sternite. epm'., epimerum of 
prothorax. eps'., episternum of prothorax. mb., 
membrane in the cervical region, j'., j"., j'"., the 
three jugular sclerites. f.l., the space for the articula- 
tion of the foreleg, ps'., presternum, st'., sternum of 
prothorax. stl'., sternellum. cxp., coxal plate, 
epm"., epimerum of mesothorax. mph"., mesophragma. 
Other letters as in Figure 1. 

The sclerites controlling the movement of the wing are 
indicated, somewhat diagrammatically, in black. 

Figure 3. The ventral plate of the ovipositor of Hasmatopota 
pliivialis. X 50. 

Figure 4. The plates which make up the dorsal wall of the ovi- 
positor of same. They are easily recognizable as 
degraded tergites of suppressed segments. X 50. 



THE THORAX OF TABAKUS 



69 



is reduced to a narrow ring into which the membrane of the neck is 
inserted, and the metathorax to a ring of only a little greater extent, 
uniting the thorax to the abdomen ; on the dorsal surface in many forms 
the whole of the wall belongs to the mesothorax. The sutures between 
the various sclerites are generally close ones. In many cases the separation 
is only indicated by a ridge on the internal surface and a narrow groove 
externally, or sometimes only by a dome-like elevation on the outer 
wall. The whole thorax forms a chitinous box, opening anteriorly 
into the neck and posteriorly into the abdomen, and is filled up 
almost entirely by the powerful muscles of flight. The various 
structures which pass from the head to the abdomen lie in the ventral 
portion of the cavity, and occupy a very small amount of the space. 

The difficulty that exists in attaching the correct names to the dif- 
ferent parts will be readily appreciated when it is stated that there 
are in existence four drawings of the thorax of the house-fly by 
entomologists of note, no two of which are named in the same 
manner. Fortunately the subject is not of great practical importance, 
and it will suffice if the discussion is confined to the practical 
points which have to do with the dissection of the fly, and to the 
nomenclature in so far as the terms are used in systematic classification. 
With regard to the latter point a good deal of difficulty is met with, for 
the terms in use by systematists are frequently very vague so far as their 
reference to the same part in different flies is concerned. 

The distribution of the various sclerites and the alteration in position 
which they may undergo will be best understood by studying a concrete 
instance first ; the thorax of Tabamis will serve as an 
example, as it occupies a more or less intermediate xiv fig 2) 

position between the extremes. In this form the 
whole of the dorsal wall of the thorax as seen externally is formed 
by the tergite of the mesothorax, which is subdivided into several 
portions by more or less distinctly marked transverse fissures. About 
the middle of the thorax, and just anterior to the wing insertion, 
there is on each side a short fissure or notch which indents the margin. 
The part in front of this is the praescutum, and the part behind the 
scutum ; the separation between the two is indistinct, and only marked 
hy these lateral notches. Behind the scutum, which is somewhat 
narrowed posteriorly, there is a stout and conspicuous triangular piece 
termed the scutellum. This projects a little above the first segment 
of the abdomen, and is distinctly demarcated from the scutum by a 
transverse fissure. This is all that can be seen on the dorsal surface 



70 



MEDICAL ENTOMOLOGY 



in pinned specimens, but if the thoracic wall is cleared in potash and 
dissected one finds at the anterior end two small elevations over- 
hanging the neck and separated from one another in front by a nar- 
row interval. These represent the two lateral halves of the tergite 
of the prothorax, and are termed the pronotum, just as the tergite of 
the middle segment is known as the mesonotum. The tergite of the 
metathorax, or the metanotum, is represented by a narrow strip of 
chitin which arches from side to side under cover of the scutellum. 
On the ventral surface of the thorax all the segments are represented, 
and in addition there are some pieces which belong properly to the 
neck, but have become displaced backwards. Starting from the middle 
line in front, the area where the thorax joins the neck is occupied by 
a loose membrane which permits of free movement of the neck on the 
body, and also permits of a considerable amount of distension when blood 
is flowing through the oesophagus. In this membrane there are three 
pairs of sclerites, none of which are united in the middle line. The 
first pair are quite free in the membrane, the second and third pairs 
attached laterally to the side walls of the thorax. These are the jugular 
sclerites, belonging to the neck. They are all small and oval in shape, 
and are not conspicuous on the external surface of the thorax, being con- 
cealed by the head. Behind them there are several sclerites closely 
pressed together and united in the middle line. These are differentiated 
portions of the sternite of the prothorax, and are termed the praesterna, 
sternum, and sternellum respectively. The praesterna are united in 
the middle line hy a thick ridge, and together form a broad trans- 
verse plate with a thickened anterior border, which limits the thorax 
in front, and to which the membraneous neck is attached. The ster- 
num is semi-circular in shape, and is wedged in behind and between 
the praesterna. Behind this there is the sternellum, a heart-shaped plate, 
closely fitted between the two sterna of the mesothorax. Arising from 
these divisions of the prosternite there is a complex arrangement of 
fibrous bands which serve to strengthen the walls of the thorax and 
to provide attachments for muscles ; these will be referred to later. 

The sternite of the mesothorax is divided only in the middle line, 
and consists of two large quadrilateral plates, which occupy about one- 
third of the total lateral area. The two plates join one another in 
the middle line at an acute angle, and so give the thorax a keeled 
appearance. Behind them there is a small oval plate representing the 
sternite of the metathorax, and behind this the first sternite of the 
abdominal wall. 



THE THORAX OF TABANUS 



71 



The sclerites of the lateral wall are comparatively simple, and can 
be homologized with the primitive type. At the anterior end there 
are two dome-shaped elevations, one behind the other, conspicuous on 
the external surface on account of the prominent tufts of hairs which 
they bear. The most anterior of these is continuous with the dorsal 
wall, and lies just below the pronotum on each side ; it may be taken to 
represent the epimeron, or dorso-lateral pleural plate. The episternum, 
or ventro-lateral plate, lies immediately behind it, and is continuous 
with the upper anterior angle of the mesosternum. Between it and 
the three divisions of the prosternum there is a comparatively wide 
interval, in which the first leg of each side is articulated ; it is on 
account of this loose articulation that the fore legs have in all Diptera 
a wider range of movement than the other pairs. Behind these sclerites 
and above the mesosternum there is the episternum of the mesothorax, 
a large plate similar in shape to the mesosternum, but smaller. The 
epimeron, if the term may be used here, does not conform to the type 
with the same exactness. It is represented by a most irregularly shaped 
plate which extends from the insertion of the wing to the middle line 
ventrally, and connects the mesothorax with the metathorax. In its 
middle third it is firmly united to the upper half of the posterior border 
of the mesosternum, but above and below this part it is attached to 
the adjacent sclerites only by a membrane, leaving a wide interval be- 
low in which the second leg is inserted. Behind its somewhat irreg- 
ular posterior border there is a narrow plate representing the fused 
pleural plates of the metathorax ; these articulate posteriorly with the 
dorsal plate of the first segment of the abdomen, and are continuous 
above with the metanotum. 

It will be noted from the above description that the wall of the 
thorax is formed from a large number of plates of different sizes and 
shapes, which are for the most part fitted closely to one another. They 
are, in fact, closely fused together to form a chitinous box, and cannot 
be separated by dissection. But at certain places the union is less 
firm, and expansion of the thoracic wall can and does take place. 
The most important of these regions is that between the mesonotum 
and the lateral wall, where there is a wide longitudinal fissure extend- 
ing from the level of the epimeron of the prothorax to the insertion 
of the wing, and passing downwards between the posterior border 
of the meso-episternum and the anterior border of the upper third of 
the meso-epimeron. By virtue of this membraneous space the dorsal 
wall of the thorax is capable of a certain amount of movement on 



72 



MEDICAL ENTOMOLOGY 



the lateral walls. The membraneous area at the junction of the tho- 
rax with the neck has already been noted. Posteriorly there is a more 
restricted area between the meso-epimeron and the meta-pleural plate, 
and another narrow strip running vertically down the wall, between 
the posterior margin of the thorax and the abdomen. 

On the internal aspect of the thoracic wall there are certain chitinous 
structures which are termed collectively the endo-skeleton ; they are, of 

course, mere ingrowths from the exo-skeleton, and are 
Thorax designed to afford attachment for the muscles and to 

give additional stability to the wall. In the prothorax 
the existence of such a structure has already been mentioned (Plate XV, 
fig. 6). It consists of two strong fibrous bands which run outwards 
and forwards from the sternite to the pleural plates, binding the 
whole together and serving to compensate for the looseness of the wall in 
the region of the attachment of the neck. The anterior of these is 
a broad and thick transverse band which arises from the whole length of 
the line between the praesterna and the sternum, and forms a wide 
arch parallel to and behind the borders of the latter. Laterally it 
terminates in a stout rounded cord. The posterior part arises from 
the lateral borders of the sternellum, and contracts to a similar cord, 
the two uniting above the articulation of the fore leg. The fibrous 
band so formed spreads out in a fan-shaped manner, and becomes 
continuous with the anterior and internal edges of the episternum of 
the prothorax, which are turned inwards and backwards to meet 
it. 

In the mesothorax there is a structure of a different kind, designed 
solely for the attachment of muscles. It consists (Plate XV, fig. 4) 
of a pair of wing-like expansions set on a Y-shaped stalk, which lies 
in the groove between the two lateral divisions of the mesosternum. 
Each expansion consists of two thin plates of chitin, separated from one 
another behind by a smaller plate perpendicular to them, but converging 
towards one another anteriorly, so that they form the boundaries of a 
boat shaped cavity. Behind the large anterior cavity there is a smaller 
one, the anterior boundary of which is formed by the same transverse 
plate which forms the posterior limit of the anterior cavitj'. Important 
muscles arise from the inner surfaces of these plates, and the structures 
which pass through the thorax rest between the arms of the Y-shaped 
strand of chitin to which they are attached. 

In the mesothorax there is a much more important structure, the 
tnesophragtna (Plate XV, fig. 1), which forms a most formidable obstacle 



PLATE XV 



Figure 1. The thorax of Chrysops dispar, seen from behind, to 
show the mesophragina. mtn'"., the metanotum. h., 
haher. p.s., posterior spiracle, p.f., post-furca. cx'"., 
coxa of the third leg. th.o., thoracic outlet, through 
Avhich the organs pass to the abdomen. mph., 
mesophragma. X 28. 

Figure 2. A halter of Chrysops dispar. x 70. 

F'igure 3. The tarsus and foot of Haeiiiatopota pliivialis. The 
empodium is pulvilliform. X 66. 

Figure 4. The apodeme of the mesothorax of Tabaiiiis albi- 
ineditis, or the medifurca. X 90. 

Figure 5. The foot of C///^a- /(7//ga7/s. Note the flange on the 
proximal part of the claw, x 500. 

Figure 6. The prosternal region of Haeinatopota pliivialis, seen 
from the inside, ps'., the presternum, st'., the sternum, 
epm'., the epimeron. eps'., the episternum. stl ., the 
sternellum. a.f., the anterior fibres, and p.f., the 
posterior fibres, which run to the side walls of the 
thorax, f.l., space for the articulation of the foreleg. 
X yo. 

Figiire 7. A leg, to show the divisions, ex., coxa. tr., tro- 
chanter, fe., femur, tb., tibia, mt., metatarsus, t., 
tarsus. 



ENDO-SKELETON OF THORAX 



73 



in the dissection of the Tabanid flies. It consists of a wide arched 

sheet of chitin, arising from the upper part of the meso-epimera on 

each side, and also from the dorsal wall of the 
, , . , . , 1 , , , , , Mesophragma 

thorax ; this extends mwards and backwards through 

the metathorax to reach as far as the posterior limit of the latter, 
the chitin from the two sides meeting in the middle line to form one 
continuous sheet, which thus cuts off the upper portion of the thoracic 
cavity from the abdomen, and leaves only a narrow interval. All the 
structures which pass from the thorax to the abdomen have to pass 
through this aperture. The purpose of this diaphragm is to afford 
additional surface for the attachment of the powerful muscles which 
provide the motive power for flight. 

The metathorax has an apodeme similar to that of the mesothorax, 
lying upon the metasternum. It consists, however, of only one sheet 
of chitin on each side. The sheets are pointed and wing-like, and 
are supported by strong ribs of chitin, which converge posteriorly to- 
wards one another, and again diverge to form a pair of stout hooked 
processes. The structure lies immediately behind the third pair of legs. 

The three structures in the middle ventral line are sometimes term- 
ed the ante-, niecii-, and post-furca, respectively. Similar structures 
are found in most insects. The mesophragma is specially well devel- 
oped in the Tabanidae, but some- arrangement of the kind is found 
in all Diptera. 

On the internal surface of the thoracic region there are to be found 

some interesting sclerites which control the movements of the wing. 

In Tahamis (Plate XIV, fig. 2) there are two distinct 

sets, an anterior and a posterior. The anterior set ^.?'.*'*!**^ 
... ... Wing base 

consists of three conical sclerites attached to one another 

by a fibrous cord running between their broad upper ends, and stretch- 
ing from the dorsal plate, just anterior to the fissure separating the 
praescutum from the scutum, to the free part of the upper border of 
the meso-epimeron. When the muscles attached to these sclerites 
contract the longitudinal fissure across which they stretch is narrowed and 
the vertical diameter of the thorax reduced. The posterior set consists 
of five very irregularly shaped sclerites, which are so articulated with one 
another, and which have their movements so co-ordinated, that when 
the wing is folded the squama is folded on the rest of the wing, 
while when it is extended the whole of the wing is brought into one 
plane. The three upper sclerites are continuous with the bases of the 
three principal veins of the wing, and the fourth with the squama, 
10 



74 



MEDICAL ENTOMOLOGY 



itself ; as will be seen from the figure, when the longitudinal rod at the 
bottom of this system of levers is rotated upwards on the fixed point 
at its anterior end, the wing is folded and the squama rotated in a 
direction opposite to the base of the wing, while when it is rotated 
downwards the squama is pushed in the opposite direction, that is, into 
the same plane as the rest of the wing. 

Taking Tabaniis as a type the composition of the thorax in the 
Culicidae and the Muscidae, representing simpler and more complex 
Mosquito arrangements respectively, may be discussed briefly. 

In the mosquitoes (Plate XIV, fig. 1), as one woiild 
expect in creatures of less powerful flight, the sclerites are composed 
of thinner and less rigid chitin. The thorax is less compact, longer 
in proportion to its breadth, and more pointed in the middle line 
ventrally, than that of Tabaniis. The three pairs of legs are also attached 
nearer together, and appear to arise, to use the words of Nuttall and 
Shipley, from the apex of a pyramid. The disposition of the sclerites is 
indicated in the figure. The prothorax is reduced, though not nearly 
to so great an extent as in Tabaniis, and consists of a large lateral 
plate, the episternum, and a small sternum which can only be recognized 
on dissection. The episterna are articulated to the cervical sclerites, 
and there is in this form also a comparatively wide membraneous area 
at the base of the neck, which can be seen to bulge when the mosquito 
is feeding. The episterna occupy a considerable part of the wall of the 
thorax, and extend as far as the first pair of legs. They bear near their 
anterior borders the curious structures known as the patagia. These are 
sausage-shaped bodies, distinctly elevated above the surface, and con- 
nected internally with the prosterna by fibrous bands, in the same 
manner as the epimera of the Tabanids are connected with the sterna 
and sternella. The membraneous interval between the dorsal and lateral 
walls of the thorax is triangular, and lies between the mesosternum 
and the lateral plate of the presternum. There is also a rather wide 
interval between the mesothorax and the metathorax. 

One point which should be particularly noted in the anatomy of the 
thorax of the mosquito is that there are two elevations posterior to 
the scutum. The first of these is by common consent called the 
scutellum, the second, which is hidden underneath the first when the 
thorax is seen from above, is the post-scutellum, a part of the dorsal 
wall of the mesothorax. This latter piece is referred to by Theobald as 
the metanotum, but this is incorrect, for, as pointed out by Nuttall and 
Shipley, there is a narrow slip posterior to this which is the true dorsal 



Psc: ' . sc. • . SCI • • • . Tntn • " . PLATE.X2I 




pst. m"b. 



75 



PLATE XVI 



Figure 1. The thorax of Stoiiioxys calcitrans. hu., humerus. 

psc"., the prescutum. sc., the scutum, scl., scutellum. 
mtn"., metanotum. t'., tergite of the first abdominal 

* segment. a.s., anterior spiracle, ep'., episternum of 

prothorax. eps"., episternum of mesothorax. cx'., 
ex"., cx'"., coxae of the three pairs of legs, ms"., 
mesosternum. epm"., epimeron of mesothorax. 
mts'"., metasternum. eps'"., episternum of 
metathorax. epm'"., epimeron of metathorax, or 
lateral plate of the metasternum. p.s., posterior 
spiracle, x 25 approx. 

Figure 2. The scales on the ptilinal membrane of Philaemaio- 
iiiyia iiisignis. X 1000 approx. 

Figure 3. The thoracic inlet of Sfomoxys calcitrans, seen from 
the inside, pn., pronotum. ap., apodeme. j., jugular 
sclerite. cl., clavicle, cx'., coxa of the first leg. i.e., 
interclavicle. a.s., anterior spiracle. h\'t., hypotreme. 
mb., membrane, pst., prosternum. x 50. 
It should be noted, as a guide in dissection, 
that the ventral margin of the inlet is much less rigid 
than the dorsal. The prosternum can be bent on its 
attachment. 



THORrAX OF MUSCID FLIES 



75 



plate of the metathorax, and should be termed the metanotum. The 

point is of importance from the systematic point of view, as most writers 

have followed the nomenclature of Theobald when describing species. 

In the Muscid flies the thorax is much rounder and more compact 

than it is in Tabanus, and is without a definite 'keel' to the ventral 

surface. The various parts are so welded together, „^ 

- , , , ,j ,1 . Stomoxys (Plate XVI) 

and the various authorities hold such divergent views 

regarding the homology of the different sclerites, that it would be 
hopeless to attempt to give an acceptable account of the subject within 
a short space. The main divisions are, however, easily recognized. 
The whole of the dorsal wall as seen externally belongs to the meso- 
thqrax. It is divided about the middle by a deep transverse fissure, 
the anterior part, as in Tabanus, being the praescutum, and the poster- 
ior the scutum. Posterior to this there is the scutellum, like that of 
Tabanus, but generally more conspicuous and pointed. The ventral 
surface is almost entirely occupied by two large quadrilateral plates, the 
mesosterna ; behind these there are several irregularly shaped plates be- 
longing to the metathorax. On the anterior aspect of the thorax there 
are two prominent convexities between the praescutum and the anterior 
end of the sternum, which represent the pronotum. On the lateral 
aspect there are two plates between the dorsal wall and the sternum ; 
the anterior of these is the episternum, and the posterior the epimeron, 
of the mesothorax. These are 'separated from one another by a 
conspicuous vertical suture. In the space anterior to and below the 
wing base, and in the angle between the episternum and the epimeron, 
there are several small sclerites, one of which is specially distinguished 
as the tegula. * 

The internal structure of the thorax resembles in general that of 
Tabanus. The thoracic inlet has, however, more definite boundaries, 
and the fibrous bands which unite the median and lateral walls behind 
the neck are well developed, and are here termed the hypotremes. 
There is a medi-furca resembling that of Tabanus, a small post-furca, 
and a mesophragma, though this is not nearly so well developed as in 
the Tabanidae. 

From the foregoing it will be evident to the reader that the ter- 
minology of the thorax is at present in an unsatisfactory state, and 
must remain so until a great deal of attention has been devoted to 
the subject. Nevertheless, some settled method of nomenclature is a 



* This term is applied by some writers to a division of the wing base. 



76 



MEDICAL ENTOMOLOGY 



necessity in descriptive work, in order to be able to denote with some 
degree of accuracy the positions of bristles, markings, etc., by means 
of which many species are identified. Terms which have a strict an- 
atomical significance can only be applied where the homology of the 
part has been determined with reasonable certainty, and cannot, however 
desirable it would be from the purely scientific point of view, be applied 
in the present state of our knowledge. To meet this difficulty a nomen- 
clature has been adopted, and is now in general use among systema- 
tists, which is essentially conventional, and in the use of which no 
anatomical definition is implied. As Osten Sacken pointed out, such 
a conventional terminology has the great advantage of offering more 
chances of fixity, and can well exist side by side with a more purely 
anatomical one, which must necessarily be modified as our knowledge 
of the structure of the Diptera increases. 

It is chiefly among the higher Diptera that difficulties are met with, 
as in the description of these it is often essential to define with pre- 
cision the positions of the large bristles or macrochaetae. Chaetotaxy 
will be dealt with later, but before doing so it will be necessary to 
describe the various regions in the current terms. The definitions 
given by Osten Sacken, who was the first to emphasise the im- 
portance of the subject in descriptive work, will be followed almost 
verbatim, as his paper, published in 1884, is not readily accessible, 
and contains an authoritative account. At the same time the terms 
employed will, as far as possible, be brought into line with those which 
have been used in the foregoing pages, using Stomoxys, of which a 
figure is given on Plate XVI, as a type. (See also Plate XIX, fig. 6.) 

The sutures which separate the various plates from one another are 

used as landmarks. Thus, the dorsopleiiral suture runs from the 

humerus to the root of the wing, and separates the 

Nomenclature mesonotum (or tergum) from the pleura. The ster- 
ol Thorax b ' i , , 

nophiiral suture is horizontal, and lies below the 

dorsopleural and parallel to it. The mesopleiiral suture runs downwards 
from the wing, and separates the mesopleura from the pteropleura. 
The mesopleura lie between the dorsopleural and sternopleural sutures, 
and therefore correspond to the episternum of the mesothorax, as indi- 
cated in the figure. The pteropleura are situated under the insertions 
of the wings and behind the mesopleural sutures. In the figure the region 
will be seen to lie between the membraneous area at the wing base and 
the posterior spiracle. It corresponds to the lateral plate of the meso- 
thorax of Lowne, the same term being employed by Gordon Hewitt in 



THE WINGS OF DIPTERA 77 

his description of Musca domestica. The steniopleura are defined as 
those portions of the mesosternum which, from their position, form a part 
of the pleura, or side walls of the thorax, in contradistinction to the 
middle portion of the mesosternum. The hypopleura are distinct pieces 
above the two last pairs of coxae, and behind the sternopleura, from 
which they are separated by sutures. The region is shown in Stoinoxys as 
the metasternum. The parts in this region are much compressed together, 
and the separate sclerites are difficult to dehne. The inetapleuni lie 
immediately above the hypopleura, and behind the pteroplcura ; this 
region is more or less convex, and lies between the root of the wing 
and the halter. Other terms in use are as follows. Scutellar bridges — 
small ligaments on either side of the scutellum which connect it with 
the mesonotum. Praesiitiiral depression — -a depression lying in the angle 
between the transverse suture on the thorax (between the scutum and 
praescutum), and the dorsopleural suture. Praealar callus — a more or less 
distinct tubercle in front of the root of the wing, and Postalar callus, a 
similar tubercle behind the wing, between it and the scutellum. The 
humerus, or humeral callus, is usually a well-marked convexity at each 
side of the anterior end of the thorax, and corresponds to the pronotum. 

THE WINGS (PLATE XVII) 

The possession of only one pair of wings, the mesothoracic^ is char- 
acteristic of the Diptera, and, as is to be expected in insects of such 
powerful flight, they are highly developed. 

A word as to the origin of the wings. They are not appendages 
in the zoological sense, but arise as outgrowths from the body wall, 
formed in the pupal stage. The small buds which first appear become 
gradually flattened out, and as they grow their substance is penetrated 
by tracheae or air tubes, which, when the wing has assumed its final 
leaf-like form, remain as veins or nervures to support the delicate 
membraneous portion. 

The wings do not vary much in shape in the different families. The 
anterior border is straight or nearly so, the apex and posterior border 
gently rounded. The posterior border is generally indented in such a 
way as to divide the wing in this region into parts which have re- 
ceived distinctive names. The indentations are found in the proximal 
half, and are known, from without inwards, as the anal lobe, (so called 
because when the wings are folded this portion of the wing lies over 
the distal end of the abdomen*) the alula, the antisquama, and the 

' This is not always actually the case. 



78 



M_EI>ICAL ENTOMOLOGY 



squama. The last named is generally a distinct portion of the wing;, 
and is much thicker and coarser than the rest, and has often a fringe 
of iine hairs around its border ; it is separated from the wing except 
at one point, and is folded underneath in repose, so as to be in con- 
tact with the antisquama, this being accomplished by a mechanism 
such as that described when dealing with the anatomy of the thorax 
of T aha nits. 

The \A ings may be simple, transparent, and more or less iridescent, in 
which case it is usual to find a row or rows of short but stout spines 
on the principal veins, or their surface may be mottled in various 
ways, as in Hacinatopota. The veins may have no other coating 
than the rows of spines, or they may bear scales of various sorts, a,s 
in the Culicinae. The scales may be all of one colour, as in the 
Citlex group, or they may be variously coloured, and impart to the 
wing the dappled appearance which is characteristic of the Anopheles 
mosquitoes. In Phlebotomiis they are covered with a dense layer of 
fine hairs. 

The veins of the wing present great and important variations in 
the different families, and the venation is, by common consent among 
Venat'on dipterologists, regarded as one of the most important 

factors in deciding systematic position. As a general 
rule the more primitive the form the more equally will the wing veins 
be distributed over the surface, and the more advanced then the more 
will they be concentrated towards the anterior border, the most ante- 
rior veins of all becoming shorter and joining the anterior margin of 
the wing at a more proximal point. The veins radiate from the nar- 
row base, where they are continuous with the sclerites which control 
the movements of the wing. The longitudinal veins are here and 
there united by short cross-veins, and, with these and the margins of 
the wing, the whole area is divided into a number of spaces called 
cells. As the veins are crowded to the anterior border the more 
anterior of these cells become reduced in a corresponding degree, the 
posterior part of the wing being left clear. 

Several systems of nomenclature have been devised with regard to the 
veins, two of which are in common use at the present time ; one of these 
has the advantage of ease of application and has up to the present 
time been the most used of any, while the other, that of Comstock 
and Needham, has the greater scientific value in that it attempts to 
bring the Diptera into Hne with other insects. It is probable that in 
the future it will replace the older method. 



NOMENCLATURE OF THE WINGS 



79 



Comstock and Needham's system may be taken first, as being the 
most easily understood, though not necessarily the most easily applied. 
These workers deduced from an extensive series of ob- 
servations a primitive condition of the venation, w hich 

^ Needham s 

they put forward as a 'urotype' (Plate XVII, fig. 1). Nomenclature 
In such a wing all the veins are to be traced to two 
tracheae, which enter the wing on the anterior and posterior borders 
respectively. Each of these divides at once on entering the wing to 
form a number of branches which traverse the long axis and ultimately' 
reach the borders. In the fully formed wing these tracheae remain 
as the longitudinal veins, of which there are four derived from each 
trachea. Taking those from the anterior tracheae first, they are named 
in order from before backwards the costa, subcosta, radius and media. 
The costa is undivided, and lies near the anterior border of the wing. 
The subcosta bifurcates near its termination, both branches reaching 
the -border anterior to the apex. The radius divides in the proximal 
third of the wing into two branches, the anterior one of which is 
continued undivided to the apex of the wing ; the posterior divides 
twice, so as to produce four branches, all of which reach the wing 
margin near the apex. The media divides into two about the 
middle of the wing, and each branch again divides in the outer 
third, so that there are four terminal branches. The posterior trachea 
also gives rise to four veins. The first of these is the cubitus, which 
divides into two about the middle of the wing, each vein so produced 
running undivided to the posterior border. The remaining veins are 
simple and undivided, and are termed the first, second and third anal 
veins. 

The types of venation seen in modern Diptera are derived from the 
urotype by coalescence of certain of the original veins with one another, 
and by the development of certain cross-veins. These unite the longi- 
tudinal veins with one another, and, with the wing borders, divide 
up the wing into areas known as cells. The difficulty in the applica- 
tion of this sj'Stem is to determine which veins have coalesced when 
the number is reduced. 

The veins and cells are distinguished by the initial letter of the 
primary vein from which they spring, followed by the numeral indi- 
cating the position of the branch, starting from the anterior side. 
Thus the first radial vein is Rl, the second R2, the first division 
of the cu-bital vein CuJ, and so on. The cells are distinguished by 
the -initial letter of the vein forming the anterior margin, preceded by the 



80 



MEDICAL ENTOMOLOGY 



corresponding cardinal number. Thus, 3rd R indicates the third radial 
cell, 2nd Cu the second cubital cell, and so on. 

The form which approaches the urotype the most closely is Phleboto- 
mtts. In the Culicidae and Tabanidae there is rather more concentra- 
tion of the veins, but in all the Orthorrapha one finds them distributed 
more or less equally all over the surface. In the Cyclorraphic flies 
the concentration is marked, and in the Hippoboscidae the posterior 
half is almost free from veins, those derived from the posterior tracheae 
having become very much reduced. 

The cross-veins which unite the longitudinal ones are placed and 
named as follows. The humeral cross-vein connects the costa and 
subcosta near the base of the wing. The axillary vein, generallj' thick 
but short, connects the veins of the anterior set at the insertion of 
the wing. The radial-median vein connects the fifth branch of the 
radial vein with the first division of the median vein. The median 
cross-vein connects the anterior and posterior divisions of the median 
vein with one another. The median-cubital vein runs between the 
fourth branch of the median vein and the first cubital. 

The older system of nomenclature is entirely empirical, and can only 

be applied to the Diptera. In it the veins are numbered and named in 

order from before backwards. The costa is the vein 

The older forming the anterior boundary of the wing, and is often 
Nomenclature , ^ ■> _ . 

continuous around the apex with the posterior border. 

The auxiliary vein or the subcosta lies behind it, and turns upwards 
to join it before reaching the apex of the wing. Then come in order 
the first, second and third longitudinal veins, arising from a common 
stem (the anterior trachea of Comstock and Needham's nomenclature), 
and behind them the fourth and fifth longitudinal veins, arising by 
a common stem corresponding to the posterior trachea. Behind these 
there is a sixth, and in some cases a seventh, longitudinal vein, which 
go to the posterior margin of the wing and correspond to the anal 
veins. The cross-veins are named as follows. The humeral cross-vein 
corresponds to that of Comstock and Needham's nomenclature. 
The anterior, small, or middle cross-vein unites the third and 
fourth longitudinal veins, the posterior or lower cross-vein the fourth 
and fifth, and the upper or supernumary cross-vein the second and 
third. The cells into which the wing is divided are named more 
or less in accordance with their position. Commencing at the ante- 
rior border, the costal cell lies between the costa and subcosta. The 
subcostal cell lies between the subcostal vein and the first longitudinal 



VENATION : ANOPHELES 



81 



vein. The marginal cell lies between the first and second, the first 
submarginal between the second and third longitudinal veins, and the 
second submarginal between the two divisions of the third longitudinal. 
The discal cell, when present, is bounded by the fourth longitudinal 
vein, and forms a convenient landmark from which to commence 
studying the venation. Unfortunately, and this is one of the objections 
to this system of nomenclature, a discal cell is defined as one in which 
the boundaries are formed by veins alone and not partly by the wing 
margin, and the cell answering to this description in one fly may not 
always correspond with that in another in its relations to the veins. 
Along the posterior border of the wing there may be one or several 
cells, called the posterior cells and numbered from without inwards. 
They are bounded by the posterior margin of the wing and the divisions 
of the fourth and fifth longitudinal veins. Near the base of the wing 
there may be two cells, limited externally by the anterior and posterior 
cross-veins, and known as the first and second basal cells. The anal cell 
lies between the fifth and sixth longitudinal veins, and the axillary cell 
between the last longitudinal vein and the wing base, and corresponds 
to the anal lobe. 

Certain other descriptive terms are in common use. When a cell 
is bounded externally by the wing margin it is said to be open, and when 
enclosed by the convergence of its two sides it is said to be closed. 
A cell formed by the bifurcation of a vein, and therefore more or less 
triangular in shape, is called a forked cell. The posterior basal cells 
are sometimes termed the first, second, and third forked cells, as for 
instance in most descriptions of mosquitoes. 

Notwithstanding the great deviations from the type which are found 
in the various families, these systems of nomenclature are not so 
difficult to work out as would appear from the foregoing account. 
With the aid of an example of each, and of the accompanying figures, 
the reader should be able to work out the venation in any of the other 
families. 

In most descriptions of mosquitoes the older nomenclature is used, and 

the wing of Anopheles (Plate XVII, fig. 2) may be taken as an example 

of this method. The costa, which forms the anterior 

, , , . , , • , , Venation of Mosquito 

boundary and is continuous around the apex with the 

thickened posterior border of the wing, presents no difficulty, nor does 
the auxiliary vein behind it. The first longitudinal vein runs straight 
from the base to the apex of the wing, without dividing. At the base of 
the wing another vein arises just below it, and runs to the distal part of 
11 



82 



MEDICAL ENTOMOLOGY 



the posterior border, and there divides into two. About the middle of 

the wing there are two other long veins, which are not directly connected 

with the wing base ; one of these arises from the first long vein and the 

other independently. These are, therefore, the second, third and fourth 

long veins. Behind them in the proximal part of the wing there are 

two other long veins, the anterior one of which bifurcates, while the 

other does not. These are the fifth and sixth veins. Those of the 

veins which bifurcate produce forked cells named according to their 

position. The anterior forked cell is enclosed by the two divisions of the 

second long vein, and the first and second posterior forked cells by the 

branches of the fourth and fifth veins respectively. The humeral and 

axillary cross-veins are not present, and there is no discal cell. The 

upper and middle cross-veins are nearly in line with one another, and 

connect the third long vein with those in front of and behind it, a 

short distance distal to its origin and about the middle of the wing. The 

positions of the junction between the costa and the auxiliary vein, 

the relative positions of the forked cells, and the point where the 

fifth vein cuts the margin, are of importance in classification. 

The venation of Haematopota (Plate XVII, fig. 3) will serve as an 

example of the application of Comstock and Needham's classification. 

The costa is conspicuous at the anterior margin, and 

Venation of ^j^^ subcosta arises in common with the vein behind and 
Haematopota 

joins the costa after a very short course. The strongest 
vein in the wing lies next behind, and is only separated from the costa by 
a narrow interval ; it gives off a branch internal to the middle of 
the wing, and then divides into two ; the lower of the two divisions 
so formed again divides, so that there are altogether four divisions 
of the radial vein at the wing margin. Of these the second represents 
the second and third divisions, the vein having failed to bifur- 
cate as it does in the urotype. The bifurcation of the lowest division 
into the fourth and fifth is peculiar, as the upper branch leaves the 
lower at a wide angle, and then immediately turns outwards, so that 
the two veins are parallel for a short distance instead of divergent. 
At the point where the fourth vein turns outwards there is a pro- 
jecting spur, which points inwards. Behind the main stem of the 
radial vein there is another vein, which bifurcates about the middle 
of the wing. The two branches so formed converge a little towards 
one another about the middle of their length, and are connected by a cross- 
vein, thus enclosing a discal cell ; the branch on the distal side bifurcates 
at the level of the cross-vein, and there are thus three divisions of the 



PLATE XVH 



Wing Venation 



Pigure 


1 

1 > 


Comstock find Needhani's I rotype 


Figure 


2. 


A nopheles. 


Figure 


3. 


Haeiuatopoia. 


Figure 


4. 


Stomoxys. 


Figure 


5. 


Glossincr. 



Reference Letters 

Comstock and Nkedham's Nomenclature 

C. ' Costa. 
Sc. Subcosta. 

R1-R5. The five divisions of the Radial vein. 

MI-A14. The four divi=;ions of the Median vein. 

Cul and Cu2. The two divisions of the Cubital vein. 

Anl-An3. The three anal veins, 

r.ni. The radial median cross-vein, 

m.cu. The median cubital cross-vein, 

cu.an. The cubital anal cross-vein. 

The cells are indicated by the initial letter of the vein in front 
of them, preceded by the cardinal number. Thus, 3rdR., the 
third radial cell. 

The Older Nomen'clature 
The Veins 



C, Sc., 


Costal and subcostal veins. The 




radial median vein. The anterior 




latter is also termed the auxiliary 




cross-vein, so called, is a super- 




vein. 




numerary cross-vein between the 


1 L— 6 L. 


The longitudinal veins. 




second division of the radial vein 


a.c.v. 


Anterior, upper, or supernume- 




and the one posterior to it. 




rary cross-vein. 


p.c.v. 


Posterior or lower cross-vein. 


ni.c.v. 


The middle cross-vein. The vein 


h. 


Humeral cross-vein. 




given this name in mosquitoes 


ax. 


Axillary vein. 




corresponds to the anterior cross- 


a.b.c.v. 


Anterior basal cross-vein. 




vein in StoiJioxys, etc., and is the 


p.b.c.\'. 


Posterior basal cross-vein. 




The Cells 




c.c. 


The costal cell. 


3 p.c. 


Third posterior cell. 


sec. 


The subcostal cell. 


4 p.c. 


Fourth posterior cell, second 


1st m.c. 


The first marginal cell. 




posterior forked cell. 


2nd m.c. 


The second marginal cell. 


1 b.c. 


First basal cell. 


sm.c. 


The submarginal cell. 


2 b.c. 


Second basal cell. 


2 sm.c. 


The second submarginal cell. 


d.c. 


Di.scal cell. 


1 p.c. 


The first posterior cell. 


an.c. 


Anal cell. 


2 p.c. 


The second posterior cell, anterior 






forked cell, first posterior forked cell. 








Lobes of the wing 




an. 


Anal lobe. 


as. 


Antisquama, or antitegula. 


al. 


Alula. 


sq. 


Squama, or tegula. 



PLATE.XVn. 



Fig. 1 




2n'J 



a. Anl 



U3iCUl 



THE HALTERES 



83 



median vein at the wing margin ; the proximal one of these, not having 
divided as it does in the urotype, represents the third and fourth. The 
cubital vein arises just below the median, but is not connected with it ; 
it divides at a point just behind the first bifurcation of the median vein, 
the two branches proceeding direct to the wing margin ; the anterior 
of these is connected with the posterior division of the median vein 
by a short cross-vein, the median cubital. There is only one anal vein, 
which arises independently behind the cubital, and reaches the wing 
margin at the same point as the second division of the cubital vein. 

The humeral and axillary cross-veins are well marked, the latter 
connecting the radial, median, and cubital veins, which are derived from 
the anterior trachea, with one another at the wing base. The radial 
median cross- vein connects" the radial vein, just distal to its first division, 
with the anterior branch of the first division of the cubital vein. The 
median cross-vein forms the distal boundary of the discal cell, and the 
median cubital cross-vein connects the posterior division of the median 
vein with the anterior division of the cubital. 

The cells will be recognized by the veins which form their anterior 
boundaries. The cell behind the fused second and third radial veins is 
the third radial cell, that behind the fifth, and limited above by the radial 
median cross-vein, the fifth radial cell. There are four median cells, the 
distal one of which is the first, while the second is divided into two parts 
by the median cross-vein. The anal cell corresponds to the anal lobe. 

In the Muscoidean flies the venation is rendered simpler by the 
coalescence and suppression of many of the veins. Much importance is 
attached to the curvature of the fourth vein, which after a downward 
and outward course for the most part of its length turns upwards towards 
the apex of the wing, either terminating at the same point as the third 
vein, and thus closing the first posterior cell, or approaching very near it. 
It should be noted that in these flies the first longitudinal vein occupies 
a position corresponding to that in which the subcosta is found in 
Haematopota. 

The halteres, or balancers (Plate XV, fig. 2) are characteristic of the 

Diptera, and are believed to be homologous with the metathoracic 

wings of other insects. They are small club-shaped 

11 , , , J , J , , J , The Halteres 

bodies, situated behind the wings and behind and 

above the posterior spiracles of the thorax. Each arises from a small 
raised cushion, the rounded end being supported on a slender stalk. 
Both the raised base and the distal end are well supplied with nervous 
tissue, the cushion consisting mainly of a highly complex arrangement 



84 



MEDICAL ENTOMOLOGY 



of sense organs. They are believed to function in regulating the flight 
and balance of the insect. 

In the calypterate Diptera the halteres are covered by the squamae. 
Except for this they do not provide characters of use in classification. 

THE LEGS 

The' legs are six-jointed, the joints being named from above down- 
wards as follows : — coxa, trochanter, femur, tibia, tarsus and metatarsus. 

They are alwaj's fairly long, and may be, as in the 

The Legs mosquitoes, very long and slender. In the purely 

(Plate XV, figs. 3, ^ u A A nj 1 

5 and 7) parasitic lorms, such as Hippobosca and Meiophagus, 

they are shorter but very stout. The relative propor- 
tions of the different joints does not vary much in the order. The 
coxa, by which the leg is articulated to the thorax, is short, generally 
oval in shape, and stout. The trochanter is a small joint which connects 
the coxa with the femur. The femur and tibia are long and generally 
cylindrical. The tarsus consists of five joints, of which the last four, 
the tarsus proper, are short, not much greater in length than in breadth ; 
the first joint is often longer than the rest, and is sometimes called the 
metatarsus. As Colonel Alcock has pointed out, the use of the word 
metatarsus in this connection is hardly accurate, as the joint referred to 
is proximal to the tarsus, not distal to it. 

The joints of the legs may be coloured in various ways, and are 
frequently banded. They may have on them prominent spines or hairs, 
which may furnish characters useful in distinguishing species. 

The foot of a fly consists of a pair of claws, with a pair of pads 
between them. The claws or ungues may be very delicate, as in the 
mosquitoes, or extremely strong and serrated, as in the Pupipara. They 
may be variously toothed and serrated, and thus yield useful distinguish- 
ing characters. All the claws may be alike, or those of the forelegs may 
differ from the other two pairs. 

Between the claws there are other structures the form of which 
furnishes diagnostic features. These are the pulvilli and the empodium. 
The former are bilateral, and consist of small elongate pads of fine 
glandular hairs, which secrete a sticky substance, said to be used by the 
fly when crawling on a slippery surface. One of these pads arises near 
the base of each claw, and the empodium lies between them. Its form 
varies a good deal in the different families ; it may consist of only a few 
moderately stout hairs, with a complex arrangement of nerve cells at its 
base, or it may consist of many hairs like those of the pulvilli, from which 



EXTERNAL GENITALIA OF DIPTERA 



8^ 



it is then not easy to distinguish ; in this case it is said to be pulviUiform. 
The pulviUi and empodium have some practical importance, for it is 
on them that bacteria may be carried from place to place by the fly. 

THE ABDOMEN 

The segmentation of the abdomen is much simpler than that of the 
other regions of the body, as each metamere is represented in the 
external wall by a pair of plates, the tergite and the sternite. These 
are transversely elongate, and in the unfed fly the tergite usually 
overlaps the sternite, thus concealing the membrane which unites them. 
Each plate overlaps the one behind it, and is attached to its neigh- 
bours by a narrow strip of membrane, which permits of movements 
of the segments on one another. The pleural membrane which con- 
nects the tergites and the sternites is lax enough to be capable of 
considerable distension when the fly is gorged with food. The num- 
ber of segments visible externally varies from eight or nine to four, and 
progressively diminishes from the more primitive to the more complex 
forms, the diminution corresponding generally with a modification of 
the terminal segments into structures connected with the reproductive 
system. The terminal segments are always reduced in size. The open- 
ing of the alimentary canal is situated between the last tergite and 
sternite. In the higher forms, along with a reduction in the number 
of segments, there is also a great reduction in the extent of the ster- 
nites, which become restricted to a narrow space in the ventral middle 
line ; the tergites are increased in extent, but not sufficiently to com- 
pensate for the reduction of the sternites, so that there is a wide lateral 
area which is occupied by membrane. In the Pupipara the division 
of the abdominal wall into segments, and the separation between the 
tergites and sternites, are to a large extent lost, and the whole abdo- 
men is enclosed by a tough but flexible integument. In these forms 
the anterior end of the abdomen is much contracted, and is joined 
to the thorax by a narrow ' waist '. 

The external genitalia consist of structures which are designed to 
assist in copulation, and, in the female, also in oviposition. They are 
formed from the terminal segments of the abdominal 
wall, and probably also from the remains of true External 
abdominal appendages. It has long been recognized (Piate XVlll) 
that these organs, especially those of the male, present 
an extraordinary degree of variability, and thus provide most useful 
distinctive characters by which forms very similar to one another 



MEDICAL ENTOMOLOGY 



may be distinguished. Unfortunately this variabiHty makes them very 
difficult to study, and the homology of the parts has not yet been 
determined with any exactitude, a circumstance which rendrs the adop- 
tion of a satisfactory terminology very difficult. The same type of 
apparatus is found in each genus, however, and the parts have been 
successfully used, in the cases of Phlebotomiis and Glossina, for the 
differentiation of species. It is evident that a classification founded 
on such definite morphological points is of much greater and more 
permanent value than one founded upon mere surface markings and 
colouration, which are not always constant for the species. 

The male external genitalia are referred to under the general term 
hypopygium. They consist of a series of bilateral hooks or claws, 
with which the male attaches itself to the female during coitus, and 
a median set of structures which includes the penis and its sheath. 
Usually there are two pairs of claw-like structures, which may be 
either concealed within the abdomen when not in use or remain per- 
manently outside ; these are termed the daspers. One pair of them, 
usually the superior, is much larger than the other. The internal 
structures lie between the claspers, and are provided with a muscular 
mechanism by means of which the penis can be protruded at will 
through its sheath ; the penis is connected with the seminal vescicles 
by an ejaculatory duct. 

The external genitalia of the male Phlehotomus (Plate XVIII, fig. 4) 
have been described by Newstead and by Annandale. They consist 

of two pairs of claspers, a sub-median lamella, certain 
External Genitalia intermediate appendages, and an intromittent organ, 
of Phlebotomus ^, , ■ , , , , ■ , 

The superior claspers are dorsal m position, and 

form large and conspicuous objects at the end of the abdomen, thus 
affording a character by which the sexes can be distinguished at a 
glance. They are composed of two segments, which, in the position 
of rest, are acutely flexed on one another, so that the terminal one 
comes to lie in the vertical axis of the body. The proximal segment 
is larger and stouter than the distal ; both are covered with a dense 
coating of hairs, and the terminal segment is provided with a series 
of large spines at the apex, to which Newstead attaches a specific value. 
The inferior claspers are smaller, and are unsegmented ; they are placed 
ventrally and oppose the superior claspers, reaching as far as or beyond 
the distal end of the first joint of the latter. They may bear spines 
at the distal end. The sub-median lamellae are thin leaf-like structures, 
which lie between the inferior claspers, and are therefore only seen 



f 




87 



PLATE XVIII 



Figure 1. 
Figure 2. 



Figure 3. 



Figure 4. 



Figure 5. 



Figure 6. 
Figure 7. 



The ovipoRitor of Miisca nehiiJo, extended, x 22. 
The distal end of the abdomen of Hippohosca tiiaciilafa, 

2 . g.o., the genital opening, an., the anal plates, one 
on each side of the anal opening. X 40. 

The genital armature of Glossina, 3 , the hypopy- 
gium being extended backwards to display it. i.e., 
inferior clasper. ed., edituni. s.c, superior clasper. 
cm., connecting membrane, h., harpes. sc ., cm'. ; 
the dotted lines indicate the position to which the clas- 
pers and the membrane can be displaced. After 
Newstead. 

Diagram of the external genitalia of Plilebotoiiiiis, 

3 , after Annandale. u., upper or superior append- 
age, ch., chaetae. f., genital filament, i., intermediate 
appendage, p., intromittent organ, s.b., subgenital 
lamella. 1., lower or inferior appendage. 

The genital armature of Tabaiiiis albiDiediiis, 3 . 
s.c, superior claspers. i.e., inferior claspers. t., tergite 
of the last segment of the abdomen, p., penis, in its 
sheath, x 80. 

One of the superior claspers of Ciilex concolor. x 100. 
The terminal segments of the abdomen of a Joblotia 
sp., 2 , forming a simple ovipositor. Note the loose 
membrane between the plates, x 60. 



EXTERNAL GENITALIA : GLOSSINA 



87 



when the specimen is mounted dorsum uppermost. The intermediate 
appendages arise from the base of the first joint of the superior clasper, 
and occupy a median position, surrounding the penis. The intromittent 
organ is the central part of the whole apparatus, and contains the duct 
from the internal reproductive organs. It is a thin rod-like structure, 
highly chitinized, and has at the upper end a small oval chitinous 
swelling, at the lower end of which it receives the ejaculatory duct ; at 
the distal end it terminates in a barbed chitinous penis. The swell- 
ing at the upper end of this organ contains much delicate muscle 
fibre, and is said to function as a pump to regulate the exit of the 
spermatozoa. 

In the Orthorraphic flies it is usual to find the external genitalia 
strictly external, and some parts of them, usually the superior claspers, 
visible without dissection, as in Phlebotomus. In the Culicidae the 
superior claspers (Plate XVIII, fig. 6) are easily seen in mounted prepa- 
rations, and their shape and the angle at which they are attached to 
the abdomen are used as characters in classification. In Tipiila and 
Asilus the male genital armature is very conspicuous, and also of a very 
complex description. In Tahaniis (Plate XVIII, fig. 5) the claspers are 
withdrawn beneath the terminal tergite, and can only be seen when 
dissected out. In the Cyclorraphic flies the parts are always concealed 
within the end of the abdomen, and can only be examined in specially 
made preparations. In Miisca and its near allies the parts usually have 
a sinistral asymetry, and are composed of a complex of chitinous plates 
which have been differentiated as tergites and sternites of suppressed 
segments of the abdominal wall. The complexity of the parts is so great 
that it would serve no purpose to give a detailed description of them 
here. Those of Glossina, however, are of importance in classification, 
and demand further consideration. 

The ventral aspect of the end of the abdomen in Glossina has on it a 
convex oval swelling, with a groove down the middle line. When the 
part is cleared in potash and dissected, it is found 
that the area of this swelling is formed by a separate ^"^^^gj 
plate of chitin, which is articulated by its posterior 
end to the ventral plate of the eighth segment of the abdomen, and is 
free for the rest of its periphery, so that it can be folded downwards 
and backwards until it projects at the distal end of the fl}-. The 
hypopygium as seen externally is in fact only the outer casing, the 
functional parts being concealed on its internal surface, and only 
displayed when the plate is everted. They consist of the following 



88 



MEDICAL ENTOMOLOGY 



parts : — superior and inferior claspers, the editum, harpes, juxta, penis, 
a median process and a connecting membrane. The superior claspers 
are the largest and most important parts of the apparatus ; they are 
stout hook-shaped organs, terminating in blunt chitinous points, which in 
many species are bifid. They are attached by their stout bases to 
that portion of the basal plate which is anterior when the hypopygium 
is closed and posterior when it is open, and are also capable of a 
limited amount of movement on their own attachments. The editum 
is a flange-like expansion, arising from the basal plate about the 
middle of its length on each side, external to the superior claspers. 
It bears a tuft of hairs. The inferior claspers are smaller than the 
superior, and are attached to the basal plate between them near 
the articulation with the eighth segment ; they are softer, and do not 
terminate in chitinous points, but bear numerous fine and long hairs. 
Newstead attaches great importance to these organs, which appear 
to vary a great deal in the different groups of species. The harpes 
are bilateral organs situated between the attached bases of the superior 
claspers, and are most conspicuous in the fusca group. They may be 
armed with small chitinous hook-shaped sclerites near the terminal 
end. The juxta or penis sheath is a median structure extending from 
the apices of the inferior claspers to the level of the bases of the superior 
ones ; it is tubular, divided and expanded at its distal end, and is, 
with the penis, everted along with the harpes. It has on each side 
a membraneous expansion, the vesica, supported by the harpes. The 
median process, when present, lies between the inferior claspers in 
the middle line, and is highly chitinized. The connecting membrane, 
present only in the palpalis and morsitans group, stretches between 
the superior claspers. 

The modifications of this highly complex apparatus will be dealt 
with in a later chapter, in connection with the species for the differentia- 
tion of which the characters which it provides are used. The structures 
in Glossina, elaborate as they are, are not more so than in other 
groups, and the great difficulty in determining the relationships and 
homology of the parts must necessarily militate against their general 
use, for the present at least, in systematic Dipterology. 

The external genital apparatus of the female is generally much 

simpler than that of the male, and consists of a tube which can, to 

a greater or less extent, be protruded from the abdo- 
External Genitalia , • , , i-, i x • 

of the Female ^ agam closed up like a telescope. It is 

only developed to a high degree in those forms in 



FEMALE GENITALIA: DIPTERA 



89 



which the abdomen is shortened, as in the Muscidae, and reaches its 
highest development in those flies, such as Miisca, which deposit 
their eggs in a soft substance. In the Orthorraphic flies it consists 
merely of some small plates of chitin, representing tergites and sternites 
of suppressed segments, which are connected together by membrane, 
and, in the resting condition, folded beneath the last visible segment 
of the abdominal wall. In the Culicidae an ovipositor as such can 
hardly be said to exist, but the terminal segments, much reduced in size, 
are closely compressed and at the same time connected together by a 
membrane loose enough to allow the plates to be extended on one another 
when the eggs are being laid. In Tahamis (Plate XIV, fig. 4) there are 
several suppressed plates under cover of the last segment, which are 
similarly attached, and can be drawn out by dissection, disclosing a 
simple ovipositor. The dorsal wall of this is formed by one broad 
plate, the tergite of the eighth segment, two small lateral plates which 
represent the tergites of the ninth and tenth segments divided into two 
lateral halves, and two anal plates, which project at the end of the 
abdomen, and represent the tergite of the eleventh segment similary 
divided in the middle line. The ventral wall is formed by a single 
plate of an irregularly quadrilateral shape, which may represent the 
sternites of the corresponding segments fused together. The greater 
flexibility of the dorsal wall allows the ovipositor to be bent downwards 
when it is in use. 

In Musca and those of its allies with similar breeding habits the 

ovipositor, when extended for use, is a tube equal in length to the 

rest of the abdomen, and of a diameter suitable for „ . . 

1 • r 1 ^1 Ovipositor of 

the accommodation of the egg. The membrane between Klusoa 

the segments is so much increased that the tube when 
fully stretched owes at least half its length to the inter-segmental 
membrane, and the segments themselves are membraneous except for 
the small sclerites in the dorsal and ventral walls which remain to 
represent the original tergites and sternites. The sixth, seventh and 
eighth segments can be distinguished, and at the terminal end there 
is a small pair of plates, one dorsal and one ventral, which correspond 
to the tergite and sternite of the suppressed ninth segment. When in 
repose each of these divisions of the tube fits inside the one anterior 
to it, and the whole organ is retracted within the abdomen. When in 
use it curves downwards and a little forwards under the abdomen of 
the fly, and is in many species actually thrust into the dung or other 
soft substance in which the fly is about to deposit its eggs. 



90 



MEDICAL ENTOMOLOGY 



In the Pupipara, which deposit their larvae on the ground, there is no 
longer any necessity for a long tube, and the external genitalia are 
reduced to a simple transverse or cresentic slit, separated from the 
anus, which is posterior to it, by a stout piece of chitin. On account 
of the large size of the larva at the time it is deposited the slit, known 
as the vulva, is structurally adapted to enable it to dilate at the 
moment of parturition, and is provided with powerful muscles for 
the purpose. Dilatation is accomplished by retraction of the posterior 
lip of the orifice, and by separation of the two lateral halves of the 
anterior lip, which is composed of two plates of chitin meeting in the 
middle line but not continuous with one another. (Plate XVIII, fig. 2.) 

The genitalia of the female flies do not provide characters used in 
classification. 

CHAETOTAXY (PLATE XIX) 

The value of the number and arrangement of the macrochaetae on the 
exo-skeleton as characters for systematic work was first recognized 
by Osten Sacken, and since the publication of his papers chaetotaxy 
has been a prominent feature in all descriptions of the higher Diptera. 
The subject is rather a difficult one, as it is often a very nice point 
to decide as to whether a particular hair shall be termed a macro- 
chaeta or not, and on which of the more or less arbitrary regions of 
the thorax it is situated. As has been stated elsewhere, the reader 
will do well to seek the advice of an expert in the determination of 
species in such a difficult group of flies as the Muscoidea, in which 
the chaetotaxy is extensively used. The following account will suffice 
to give some idea of the subject, and to enable the student in most 
cases to separate the different genera. The distinction between many 
species in this group depends on such fine points that an actual com- 
parison of the specimen with the type or a co-type is frequently 
necessary in order to identify it. 

The bristles are named according to the situations in which 
they occur, the terms used being mainly those which have al- 
ready been enumerated in connection with the structure of the exo- 
skeleton. 

On the head : — Commencing from the front, the vibrissae are a pair 
of stout and prominent bristles situated one on each of the prominent 
anterior lateral angles of the epistomal orifice, called variously the 
' oral margin ' or ' buccal orifice '. The epistomal bristles are situated 



PLAT£.m. 



ph. dc. a. dc. ph. nu. 




91 



PLATE XIX 



Chaetotaxy 

Figure 1. Diagram showing the dorsal thoracic bristles, after 
Williston. 

Figure 2. Thorax of Miisca domestica, dorsal side. 
Figure 3. Thorax of GJossiua palpalis, dorsal side, after Austen. 
Figure 4. Thorax of Stonioxys calcitrans, lateral aspect. 
Figure 5. Thorax of Glossiria palpah's, lateral aspect, after 
Austen. 

Figure 6. Diagram of the parts of the thorax, after Mik, from 
Osten Sackeii. p., pronotum. s., scutellum. m., 
metanotum. 1. dorsopleural suture. 2. sternopleural 
suture. 3. mesopleural suture, a., mesopleura. b., 
pteropleura. c, sternopleura. d., hypopleura. e., 
metapleura. I. dorso-humeral region. II. dorsoalar 
region. III. dorso-central region. 

Figure 7. Head of Miisca domestica, seen from above. 



a. 

as. 

acs. 

asp. 

dc. 

Idc. 

2dc. 

fo. 

hu. 

ia. 

mp. 

msc. 

npl. 

oc. 

pa. 

ph. 

pr. 

psp. 

psdc. 

psc. 

pt. 

pv. 

sa. 

V, 



Reference letters, figure 6 excepted. 

Acrostichal or inner dorsocentral bristles. 

Anterior spiracle. 

Apical scutellar bristle. 

Anterior sternopleural bristle. 

Dorsocentral bristles. 

First dorsocentral bristle. 

Second dorsocentral bristle. 

Fronto-orbital bristles. 

Humeral bristles. 

Intra-alar bristles. 

Mesopleural bristles. 

Marginal scutellar bristles. 

Notopleural bristles. 

Ocellar bristles. 

Post-alar bristles. 

Post-humeral bristles. 

Prae-sutural bristles. 

Posterior sternopleural bristles. 

Prae-sutural dorsocentral bristle. 

Prae-sutural dorsocentral bristle. 

Pteropleural bristles. 

Post-vertical bristles. 

Supra-alar bristles. 

\'ertical bristles, 



CHAETOTAXY 91 

on the peristomalia, which are ridges on the lower edges of the peristoma, 
or the cheeks, regions which correspond to those described as the genae. 
The facial bristles, often very conspicuous, are situa- 
ted on the front of the head, external to the antennae, ^r."?*',^^. 

(Plate XIX, fig. 7 & 

and above the vibrissae. The lateral facial bristles, pi^te in, fig. i) 
when present, are external to them and on the lower 
part of the head. The frontal bristles are situated on the upper part 
of the head, external to the ptilinal suture, on each side of the inser- 
tion of the antennae, and above and external to the facial bristles ; the 
rows of the two sides converge towards one another near the vertex 
of the head. There may be two pairs of vertical bristles, an inner and 
an outer, at the upper and inner angle of the eye, and there may be 
post-vertical bristles behind them. In front of the vertical bristles, and 
behind the frontal bristles, there are three sets of fronto-orbital bristles, 
upper, middle and lower, the last named being rarely present ; the first 
are always reclinate, and may appear as a continuation of the frontal 
rows posteriorly ; the second are always proclinate and are generally 
nearer the orbit. The ocellar bristles are situated in the ocellar triangle 
at the vertex of the head ; post-ocellar and prae-ocellar bristles may be 
present. The facio-orbital bristles are situated, when present, on the 
narrow strip between the eye and the lower half of the ptilinial suture. 
There may also be bristles on the cheeks. 

On the thorax : — Humeral bristles are situated on the humeral callus, 
and post-humeral ones on its inner margin. The notopleural bristles, 

usually two on each side, are situated on the edge of 
, . , , , . Thoracic Bristles 

the praescutum near its posterior borders, that is to say, (Plate XIX) 

between the humerus and the root of the wing. The 

prae-sutural bristles are placed near the lateral borders of the praescutum, 

just in front of the suture between it and the scutum. On the scutum 

there are the supra-alar bristles, immediately above the root of the wing, 

usually three in number, and the intra-alar, internal to them. In the 

middle portion of the thorax there are two rows of bristles on each side, 

extending through the praescutum and the scutum. The inner two rows 

are termed the acrostichal bristles, the outer two the dorsocentral. The 

post-alar bristles lie behind the base of the wing, and behind and below the 

supra-alar. On the margin of the scutellum there is a row of scutellar 

bristles, and there may be also others removed from the margin. On 

the side of the thorax there are the propleural, immediately above the 

coxae of the forelegs ; the mesopleural, on the mesopleura, near the 

angle between the dorsopleural and mesopleural sutures (or, using other 



MEDICAL ENTOMOLOGY 



terms, on the episternum of the mesothorax, near its upper and posterior 
angle) ; the sternopleiiral , on the mesosternum, below the suture between 
it and the episternum (mesopleura) ; pteropleural, rarely present ; meta- 
pleiiral or trichostichal, on the metapleura ; and hypopleiiral, usually 
small, on the hypopleura. 

On the abdomen : — Marginal bristles, situated on the posterior margins 
of the tergites ; discal, on the tergites but removed from the margins ; 
and lateral, near the lateral margins of the segments. 

The following terms are used to denote the inclination of the bristles 
or groups of bristles -.—erect, siiherect, proclinate, reclinate, convergent, 
decussate, or cruriate. The bristles themselves are described as strong, 
weak, represented by hairs, hair-like, or normal with hairs among the 
bristles. The arrangement of a group may be in a single row, in more 
than one row, parallel, convergent, or divergent ; they may be apical, 
as on the scutellum, or sub-apical ; arranged in pairs or singly. The 
actual number is always stated unless large. 

The application of the above nomenclature requires a good deal of 
experience, and it is of great advantage to obtain a few named and de- 
scribed specimens, and to compare the chaetotaxy with the description 
of the fly by a recognized authority. 



CHAPTER II 



SECTION 2 

THE INTERNAL ORGANS 

THE MUSCLES 

The muscles serve to move the appendages on the body, and the 
joints of the appendages on one another ; they also bring about move- 
ments of one segment on its neighbours, and of the separate plates of 
the exo-skeleton of each segment on one another, when these are not 
fused together. They always arise from the internal surface of the exo- 
skeleton, and the joint over which they act may be, as in the legs, a 
more or less definite articulation formed by a moulding of contiguous 
parts of the chitinous wall, or it may be merely a space in which the 
exo-skeleton is represented only by a flexible membrane, such as exists 
between the segments of the abdomen. 

The peculiarities of the structure of insect muscle have been frequently 
described, and need not be dealt with here, as they do not concern 
the parasitologist. There is one physiological feature, however, which 
is of great importance in relation to the mechanism of feeding and 
of flight, namely, the capacity which insect muscle possesses for a 
very high degree of rapidity of contraction. It is stated by Marie 
that the wing of the fly can make 330 contractions per second, a 
rate which is probably not equalled by any other creatures, and it is 
this capacity which enables it, with a comparatively small wing area, 
to support a weight which must be relatively enormous. Similarly, 
it is the capacity of the muscles for rapid action which enables the 
mouth appendages of the blood-sucking forms, with a comparatively 
small armature and a limited excursion, to act as an extremely rapid 
and effective piercing apparatus. 

The muscles of the mouth appendages have already been sufficiently 

described in connection with the parts on which they act. The 

antennae and palps also possess small muscles, which 

, , , .... - Arrangement of 

are able to produce a limited amount oi movement Muscles 

of the joints upon one another, and of the whole 



04 



MEDICAL ENTOMOLOGY 



appendage upon the head. The muscles of the legs pass from above 
downwards, those of the first joints arising in the ventral part of the 
thorax from apodemes or chitinous protuberences, and passing into 
the tubular space enclosed by the integument of the leg. In the 
remaining joints the muscles arise above, and are inserted below, the 
articulation on which they act. 

The muscles of the body wall are arranged primarily in two sets, 
acting, so far as the shape of the body is concerned, in opposition to 
one another. One set is more or less circular, and connects the 
separate plates of the segment in which it lies ; by approximating them 
it reduces the transverse diameter of the body, with a corresponding 
increase in the long diameter. The other, which is internal to this, 
connects the segments with one another, running in an antero-posterior 
direction, so that its contraction diminishes the length of the body 
by approximating the segments. This primitive arrangement is altered 
in a characteristic manner in the three regions of the body. 

In the head the exo-skeleton of all the segments has become welded 
to form a chitinous box, the walls of which permit of no movement. 
The muscles of the body wall have, therefore, disappeared altogether. 
There are a few small bundles in the lateral walls of the neck, which 
suffice to move the head on the thorax. 

In the thorax the muscles are very greatly enlarged, and modified 
in their arrangement, in order to provide the motive power for flight, 
and it is on account of their large mass that the thorax in the Diptera 
is so conspicuous. They fill up almost the whole of the cavity, the 
various structures which pass through it being compressed into the 
ventral angle. (Plate XX, fig. 2.) 

Flight is accomplished by rapidly repeated alterations in the vertical 
and longitudinal diameters of the thorax, which impart a vibratory move- 
^ ment to the wings, and since the wings of the Diptera 

are mesothoracic outgrowths, it is the muscles of the 
mesothoracic segment which have been specially developed. It was 
pointed out in connection with the anatomy of the thorax that this 
segment has become increased to such a disproportionate extent as to 
reduce the segments in front and behind to mere rings of chitin, and 
that it is separated from the metathorax by a diaphragm-like in- 
growth, the mesophragma. It is in the space anterior to the 
mesophragma that the main mass of the muscle is contained, the 
muscles of the other two segments, except those of the legs, being 
reduced to very thin sheets. The muscles of the mesothorax con- 



MECHANISM OF FLIGHT 



95 



sist of an external set which pass somewhat obUquely downwards and 
backwards from the dorsal to the ventral wall, and a longitudinal 
set, which pass from the anterior end of the thorax to the meso- 
phragma, in the upper two-thirds or more of the cavity. It will 
be recalled that the dorsal and lateral walls of the mesothorax are 
not welded together by continuity of their chitin, but that there is a 
lateral area between them where the wall of the thorax is membraneous, 
thus permitting of some alteration in the shapes of the cavity ; and 
that there is a separate mechanism, consisting of a set of chitinous 
rods arranged as a system of levers, by means of which the wing can 
be brought into position for flight. 

Now when the wing is in position for flight, the veins project for 
a short distance within the cavity of the thorax, and are so arranged 
that the muscles act on them as on a lever, the longitudinal muscles, 
which increase the vertical diameter of the thorax, causing a downward 
displacement, and the antero-posterior set a corresponding upward dis- 
placement. If the wing surface presented a uniform resistance to the 
air throughout its area nothing would result from this, but this is 
not the case, for the veins of the wing are always stronger in its 
anterior portion, and this part consequently yields less to the pressure 
than the part behind it. In this way the surface becomes an inclined 
one, and the vibratory movement is therefore accompanied by transla- 
tion. The mode of propulsion through the air has been aptly compared 
by Marie to that by which a boat is moved through the water by a 
waterman's scull. 

It is evident that, within certain limits, the more the anterior veins 
are strengthened and the posterior ones reduced the more effective 
will the blade-like action of the wing become, and we have here a 
confirmation of the dictum of Williston, that flies with such a venation 
are more highly organized and more recent than those in which the 
wing veins are distributed evenly over the surface. We may contrast 
the two extremes of Phlebotomus and Hippobosca, the former of which, 
notwithstanding its large wing area in proportion to the body weight, 
is a feeble flier, while the latter, even when it contains a full grown 
larva, is extremely active when on the wing. 

In the abdomen the arrangement of the muscles is simpler, and 
corresponds with the more primitive structure of the body wall. The 
vertical muscles are only feebly developed, and connect the tergite and 
sternite of each segment with one another, the longitudinal muscles 
connecting adjacent terga and sterna in a similar manner. The two 



96 



MEDICAL ENTOMOLOGY 



sets move the abdominal segments on one another, and can flex the 
abdomen downwards, as in oviposition. Possibly they also assist, after 
the manner of the abdominal muscles in mammals, in the expulsion 
of the ova. They also provide the motive force for respiration. 

THE RESPIRATORY SYSTEM (PLATE XX) 

In insects respiration is carried on by a system of tubes which 
has many analogies with the arterial system of vertebrates. The 
tubes open on the surface of the body, and are there in communication 
with the external air. As they pass inwards they divide into innumer- 
able branches, which, progressively diminishing in size, conduct the 
air into the innermost interstices of the tissues for the supply of 
the body cells. Those tissues in which the metabolism is the most 
active, as for instance the mid-gut, in which digestion takes place, 
and the ovaries, receive the largest supply of air. 

The external openings through which the air enters the tracheae 

or air tubes are termed the spiracles or stigmata. Normally one would 

expect to find one pair to each segment, and this 
Spiracles ^ . . , , . ° 

arrangement is, m fact, tor the most part preserved, but 

some have been suppressed on account of the shortening of the body. 

In the head, in which no respiratory movements can take place, there are 

no spiracles, nor are there any in the very much reduced prothorax. 

The meso-and meta-thoracic segments have always a pair each, that 

of the former being the largest in the body. In the abdomen the 

anterior segments have a pair each, but the reduced segments at 

the posterior end, and those segments which are modified to form 

the external genitalia, are without them. The number of abdominal 

spiracles is naturally less in the Cyclorrapha than in the Orthorrapha, 

and the size of the tracheae from the thoracic spiracles is increased 

to a commensurate extent. 

The situation of the thoracic spiracles differs a little in the two 

divisions of the Diptera. In the Orthorrapha, in which there is a distinct 

membraneous interval between the dorsal and lateral walls, the anterior 

spiracle is usually situated at the anterior end of this interval and is 

separated from the chitinous portion of the thoracic wall. The posterior 

or meta-thoracic spiracle is placed in a similar membraneous area between 

the lateral plates of the mesothorax and metathorax. In the Cyclorrapha, 

in which the consolidation of the thorax has proceeded further with the 

development of a more powerful and rapid flight, the membraneous 



THE TRACHEAE 



97 



areas are much reduced, and the spiracles are displaced so as to lie 
between contiguous lateral plates, to which they are closely connected by 
strong bars of chitin. Each spiracle is an oval or dumb-bell shaped open- 
ing, the margin of which is maintained by a rim of chitin, more or less 
thick in accordance with the density of the rest of the thoracic wall. 
The opening is guarded by a series of teeth of various forms, designed to 
prevent the ingress of solid particles ; they may be simple and comb- 
like, or extremely minute, thin, and numerous, arising from a large 
number of short common trunks and bending in all directions across the 
opening like the branches of a tree. (Plate XX, fig. 5.) Posterior to the 
opening there is 'a small vestibule, provided with a simple valve and 
muscle, by means of which the size of the inlet can be regulated. 

The abdominal spiracles lie in the membrane between the sternites and 
tergites. Each is placed a little anterior to the segment to which 
it properly belongs, and the number is usually less than the number 
of v'sible segments. The first pair lie close to the distal end of the 
metathorax. They resemble the thoracic spiracles in structure, but are 
generally smaller. The abdominal spiracles do not, however, diminish 
progressively in size as one might expect, the largest being usually 
that which admits the air destined for the supply of the ovaries. 

In a primitive arrangement of the parts each pair of spiracles would 

give rise to a pair of branching tracheal tubes for the supply of the 

segment, but in the complex imago of the Diptera 

^, J 1 1 1 • • f , • , Arrangement 

there is a considerable deviation from this type, due Qf Tracheae 

partly to the suppression of some spiracles and their 

tracheae, and partly to the dislocation of others from their segments 

in a forward direction. The system is rendered more complex by 

the anastomosis of the branches of one tracheae with those of its 

fellow of the opposite side and with those of the adjacent segments ; the 

anastomosis takes place, not between the ultimate divisions, but between 

tracheae of considerable size. In the main features, however, the segmental 

arrangement is preserved, and most of the branches from a spiracle go to 

supply the tissues of the segment to which it belongs. 

The distribution of the main branches will be understood sufficiently 

well from the figures given. (Plate XX.) The head receives its supply 

from the anterior or mesothoracic spiracles by means of a pair of 

tracheae which pass through the neck. The two thoracic spiracles 

supply the huge mass of muscle contained within the thoracic cavity, 

and also the legs; some branches from the posterior spiracle pass into the 

abdomen and anastomose with the abdominal tracheae. Each abdominal 

13 



98 



MEDICAL ENTOMOLOGY 



spiracle gives rise to a short trunk, which divides almost at once into 

a number of branches, some of which break up for the supply of the 

adjacent viscera and the body wall, while others pass backwards and 

forwards to anastomose with the tracheae from the adjacent spiracles. 

One branch passes straight across the body immediately below the dorsal 

plates, there anastomosing with its fellow of the opposite side to form a 

loop below the heart. 

In the great majority of the air tubes, at least in the Orthorrapha, the 

diameter is uniform, and is reduced in a simple manner at each bifurcation, 

_ but in certain parts there are dilatations, in which, as 

Air Sacs .„ , ^ , , • ,• , r 

will be seen presently, the specialized structure oi 

the wall of the tube is not found. In Tahaniis there are two of these air 

sacs in the anterior end of the abdomen, which, on account of their 

white colour and large size are very conspicuous when the abdomen is 

opened without damaging them. They always contain air, but are not 

distended to such a degree as to make their walls taut. The tracheae of 

the head have always a large number of air sacs on them, especially in 

the region of the brain, and these have an important function in relation 

to the mechanism of feeding, as already described. In the Cyclorraphic 

flies (Plate XX, fig. 6) almost all the main branches of the thoracic 

tracheae are dilated to form sausage-shaped sacs, from which small 

tracheae are given off, these breaking up at once into a large number of 

branches for the supply of the adjacent tissues. One of the branches 

from the anterior spiracle on each side passes into the abdomen, and 

there dilates into a large sac, which occupies a considerable proportion 

of the abdominal space. (Plate XX, fig. 6.) 

The structure of the tracheae and air sacs will be best understood by a 

reference to their mode of origin. They represent invaginations of the 

ectoderm, and as such are lined, from the spiracle to 
Structure of . 
Tracheae ^"^^ divisions, with chitin which is continuous 

with that of the exo-skeleton. Their outer surfaces, 

that is, those which are in contact with the body contents, are lined 

by a layer of cells which is continuous with the hypodermis or chiti- 

nogenous layer of the exo-skeleton. The internal lamina consists 

of a very thin but uninterrupted layer of chitin, but in all except the 

most minute tracheae this is modified in a remarkable manner to form 

the well-known spiral thread. (Plate XX, fig. 4.) When examined under 

a high magnification, and preferably after some preliminary maceration 

in potash, the wall of the tube is seen to be traversed by a large number 

of extremely thin annular threads, which pass four or more times round 



PLATE XX 



Figure 1. The respirator^' system of Culc.x. dr., cervical 
trachea, a.s., anterior spiracle, with its large trachea, 
p.s., posterior spiracle. d.a., dorsal arch, running 
below the heart, l.tr., lateral trachea, a.tr., trachea 
anastamosing with one from the next spiracle : simi- 
larly' in the other segments. The abdominal spiracles 
are numbered in order. 

Figure 2. A section through the thorax of Haeuiatopofa, to 
show the muscles, l.m., the longitudinal muscles, 
v.m., the vertical muscles, tr., trachea, d.c, the 
duct of the crop, sl.g., the salivary glands, pv., 
proventriculus. n., nerve cord. Note the membra- 
neous area in the lateral wall, x 45 about. 

Figure 3. Respiratory system of Tabanus. br., brain, a.s., air 
sacs, ab.s., first abdominal air sac. ab.s'., second 
abdominal air sac. Other letters as in Figure 1. 

Figure 4. A trachea, highly magnified, to show the spiral thread, 
and the nuclei of the hypodermal cells which lie on 
the visceral surface. 

Figure 5. The anterior thoracic spiracle of Miisca, to show the 
fine arborescent filaments of chitin which guard the 
entrance to the trachea. x 440. 

Figure 6. The tracheal sacs supplied by the anterior thoracic spir- 
acle (a. th.). In this figure the tracheal sacs supplied 
by the posterior thoracic spiracle and the sterno-dor- 
sales muscles of the left side have been removed. 
The first abdominal segment has been removed to 
show the large abdominal air sacs (ab. s.) and an 
abdominal trachea which is supplied by the second 
abdominal spiracle (a. sp.). After Gordon Hewitt. 
A. c. s., anterior cephalic sac. a.v.s., anterior ventral 
thoracic sac. c.tr., cervical tracheal duct. d.c, 
dorsal cephalic sac. do., dorsales muscles. H., 
haustellum. l.tr.s., longitudinal tracheal sac. p.c.s., 
posterior cephalic trachea! sacs, p.v.s., posterior 
ventral thoracic sac. p. op. periopticon. Ros., Ros- 
trum, v.c.s., ventral cephalic sac. 



I=>lAte:.xx. 




RESPIRATION 



99 



the lumen in a corkscrew-like manner, the turns being so closely 
compressed together that they appear to be transverse. Where each 
length of thread ceases there is a short interval, after which another 
arises ; the threads never pass into the branches, nor do they ever 
bifurcate. When seen in sections of the larger tracheae the thread 
projects a little into the lumen, giving it a ridged appearance. The 
intervals between the turns of the thread are filled in by a very thin 
layer of chitin. 

The arrangement of circular or spiral thickenings in the wall of 
a thin chitinous tube is one admirably adapted to ensure that the 
lumen of the tube will be kept open even if the angle at which it is flexed 
becomes greatly altered ; in other words, to prevent occlusion by kinking. 
Such occlusion might readily occur in the tracheae during the move- 
ments of the body, or when the mid-gut or crop is distended with blood. 

The outer or hypodermal lamina of the tracheal wall, which is in 
contact with the internal organs, is very thin, and is only recognized by 
the scattered nuclei which lie on the surface of the tubes. It is con- 
tinued to the most minute branches of the tube, after the spiral thread 
has ceased, and as it reaches to the intercellular spaces while still in 
continuity with the hypodermis, it forms a sort of peritoneum, within 
which the internal organs are contained. 

The structure of the air sacs is essentially the same as that of 
the tracheae. There is, however, no spiral thread, and the layer of 
chitin may be greatly thickened. In the sacs of the head, and to a 
lesser extent those of the thorax in the more specialized flies, the 
wall is very dense and tough, and, as it is often adherent to surrounding 
tissues, the sacs are in some cases extremely difficult to dissect away 
from the soft parts. The sacs in the abdomen are as a rule very 
thin-walled, and have a dead white colour and a peculiar waxy appear- 
ance. When ruptured in saline solution the wall of the sacspreads out 
just as do very thin paraffin sections. 

In addition to their function of conveying air to the tissues the 
tracheae are put to another use, in that they serve to support the internal 
organs and to retain them in position. Their flexibility enables them 
to adapt their position to that of an organ of changing dimensions, 
such as the mid-gut. 

The movements of respiration in insects depend on the contraction 

of the longitudinal and vertical muscles, and are mainly restricted to 

the abdomen when the fly is in the resting position. „ . 

... Respiration 

The exact mechanism is not clearly understood, but 



100 



MEDICAL ENTOMOLOGY 



it is probable that the total capacity of the body cavity is diminished 
by the contractions of these muscles, with the result that the air is 
expelled ; inspiration is accomplished by the elastic recoil of the spiral 
thread, which restores the trachea to its original form. The air sacs 
would appear to play an important part in this mechanism. 

The chitinous nature of the wall of the tracheae and air sacs is of 
the greatest importance from the point of view of technique. Ordinary 
fixatives will not penetrate through chitin, and, even if the fluid were to 
find its way through the spiracles, it is still shut off from the soft tissues. 



THE ALIMENTARY CANAL 

The alimentary canal in its simplest form is a straight tube com- 
mencing at the mouth and running backwards through the body to 
terminate at the anus, which is situated at the extreme posterior end 
of the abdomen. Some parts of this are specialized for one function 
and some for another, and in most Diptera the tube has outgrown 
the body cavity in which it lies, and has become twisted and coiled 
upon itself. It is held in position by the tracheae which supply it 
with air, and lies in the median position, that is, below the dorsal 
vessel and above the ventral nerve chain. 

A proper conception of the morphology of the alimentary tract 
can only be obtained by reference to its mode of origin. In the 
developing embryo insect the tract consists of three 

Development 

parts, which arise in different ways. At each end 
of the embryo there is an invagination of the cuticle, which proceeds 
until two deep pits are formed ; that at the anterior end is termed 
the stomodaeum, and that at the posterior end the proctodaeitm (Plate 
I, fig. 3). Between them a cleavage occurs in the mesoblast, and this 
develops into a cavity, which in time becomes continuous with the 
stomodaeum and the proctodaeum, so that a complete canal is formed 
opening at the anterior and posterior ends of the body. The distinction 
between these three parts influences both their structure and their 
function, and should always be borne in mind. The invaginations 
of the cuticle are lined with a chitinous layer which is continuous with 
the integument, and can take no part in the actual processes of digestion, 
whereas the middle portion, or mesenteron, has no such layer, and is 
the true stomach or digestive chamber. It is lined with a specialized 
epithelium, and may be otherwise modified in connection with the 
digestive process. ..." 



DIVISIONS OF THE ALIMENTARY TRACT 101 



The alimentary tract in the adult insect is divided into a number 

of parts, each of which is more or less specialized for a particular 

function. The arrangement in the Diptera does not . . 

° . ^. Divisions 

differ much from what is found in other insects, except 

in the details of structure, and the homology of the parts is as a rule 
easily made out. The parts may be enumerated as follows : — 

[ The Buccal cavity, with the epipharynx and 
hypopharynx. 
The Pharynx. 
The Oesophagus. 
The Crop, or food reservoir. 
The Proventriculus, homologous with the 
gizzard of insects which take solid food. 



Developed from the 
Stomodaeum. 



Developed from the j ^j^^ Mid-gut. 
Mesenteron. I 



The Intestine, or Hind-gut, which may be 
Developed from the J divided into a proximal part, the Ileum,, 
Proctodaeum. i and a distal part, the Colon. 

' The Rectum. 

The three divisions are also known as the fore-gut, mid-gut and 
hind-gut respectively. It should be noted that these terms have a 
definite morphological significance, and are not to be used merely with 
reference to position. In the Muscid flies the term ' Intestine ' is 
applied to a part of the mesenteron ; confusion will not arise if the 
position of the Malpighian tubes is kept in mind. 

In addition, there are two sets of structures accessory to the aliment- 
ary tract, namely, the salivary glands, connected with the stomodaeum, 
and the Malpighian or urinary tubules, inserted into the proctodaeum. 

All the above parts can be distinguished in the Diptera. As regards 
the length of the canal, there is a progressive increase, and a tendency 
to the formation of a tube with a uniform diameter throughout, as 
one passes from the simpler Orthorrapha to the Cyclorrapha, and 
at the same time an increase in the length of the salivary glands. 
In the Culicinae the alimentary tract when drawn out is only a little 
longer than the body of the fly, while that of Miisca is three or more 
time the length. 

The buccal cavity and the pharynx have already been described 
in connection with the mouth parts. Together they form the sucking 
apparatus by which the food is drawn from the wound up the canal in 
the proboscis and passed on to the oesophagus. - - 



102 



MEDICAL ENTOMOLOGY 



The oesophagus is a simple tube, which connects the pharynx in the 
head with the proventriculus in the thorax. Immediately after it leaves 
the pharynx it passes backwards through the brain, and after reaching 
the thorax it divides into two branches of about equal size ; one of these 
passes into the proventriculus, while the other is continued onwards 
through the thorax as the duct of the crop or food reservoir. The latter 
is a thin-walled sac, capable of considerable distension, situated in the 
abdomen. The proventriculus, when present, lies either in the posterior 
end of the thorax or at the anterior end of the abdomen, and often has 
a considerable amount of muscle in its wall. It is the homologue of the 
gizzard of other insects, but as the Diptera have no solid food to grind 
it has no internal teeth, and appears in many forms to function as a 
valve. The mid -gut is the main digestive part of the alimentary tract, 
and is lined by a columnar secreting epithelium. It is capable of great 
distension in some forms. The separation between the mid-gut and the 
hind-gut, in the less specialized forms at least, is marked by the inser- 
tion of the Malpighian tubes into the wall of the canal. Posterior to the 
mid-gut the canal may be coiled and twisted to a considerable extent, 
owing to the disproportion in length between it and the cavity in which 
it lies. The upper part is generally the narrowest, and may for the sake 
of convenience be termed the ileum, the lower and wider portion being 
known as the colon, though it is important to note that these are mere 
terms of convenience, having no definite morphological significance, and 
cannot be applied in all cases. In the Muscid flies other terms are in 
common use to distinguish the different regions. The last portion of 
the canal is dilated to form a pear-shaped rectum, in which there are 
certain curious trumpet-shaped bodies called the rectal glands or rectal 
papillae. 

There is a good deal of variation in the shape and structure of 
the alimentary canal in the two main divisions of the Diptera, and it 
will be convenient to treat them, to a certain extent, separately. The 
modifications found in the higher forms are due mainly to the increased 
length of the canal, and to its more uniform calibre. 

Tabanus will again serve as an example, as it is fairly easy to obtain 
and has a simple alimentary tract (Plate XXI). 

The oesophagus commences at the posterior end of the pharynx, 
and at once narrows down to a thin tube. It first passes straight 
backward through the middle of the brain, emerging at its lower border. 
It then passes through the neck, lying at first between the two main 
nerve trunks which pass from the brain to the thorax, and later upon 



ALIMENTARY TRACT OF TABANUS 



103 



the single trunk formed by the fusion of these, a point which is well 
demonstrated in serial sections. After entering the thorax it divides 
almost at once into two branches, one dorsal to the 

other, the dorsal branch being in the same line with *''"'entary Tract 
' ° of Tabanus. - Oeso- 

the cervical portion of the oesophagus. The two phagus 

branches are equal in calibre, but differ greatly in 
length. The dorsal one runs straight through the thorax as the duct 
of the crop, while the ventral one terminates after a very short course 
by entering the proventriculus just behind its anterior end. The oeso- 
phagus, in fact, appears to end undivided in the dorsal surface of the 
proventriculus, and the duct of the crop to leave it at the same point. 
The two openings are situated on a slight elevation in the dorsal wall of 
the proventriculus. 

At the commencement of the oesophagus no cellular lining can be 
distinguished, and the wall appears to consist only of an unstainable 
chitinous membrane, but as the tube leaves the brain it comes to have 
a layer of thin and flattened cells underneath the chitin. As the tube 
passes through the neck the cells become more numerous and more 
regularly arranged, until there is a regular layer of squat cubical cells, set 
on a distinct basement membrane, while the chitinous intima is at the 
same time reduced in thickness. The basement membrane of the cells, 
which are, of course, hypodermal in origin, is of considerable thickness. 

The duct of the crop is precisely similar to the thoracic portion of the 
oesophagus, except that its lumen is a little narrower. 

The crop is a small bi-lobed sac with an extremely thin wall. This is 
composed of a single layer of very small flattened cells, external to which 
there are many small muscle fibres arranged in an 

Crop 

irregular network. From what has been said with 
regard to the relations of the two divisions of the oesophagus it will 
be evident that the crop is in a direct line with the posterior end of 
the pharynx in the head. 

The function of this sac is a little difficult to determine. It often 
contains a few small bubbles of gas, and is as frequently empty and 
collapsed, when it assumes the shape shown in the figure. (Plate XXI, 
fig. 1.) The present writers, in the course of several hundred dissec- 
tions, have never found it to contain fresh blood even in flies killed 
while in the act of feeding, though on rare occasions a little pigment, 
presumably derived from blood, has been seen in it. In freshly-killed 
flies, taken in the act of feeding and with the mid-gut filled with blood ; 
its walls can often be seen to contract in a peristaltic manner, such as 



104 



MEDICAL ENTOMOLOGY 



would result in expelling its contents. The view most consistent with 
the anatomical appearances is that it acts as a primary receptacle for 
the blood, which is passed into it direct from the pharynx as it is 
sucked up, and is passed on into the mid-gut by the contraction of the walls 
of the sac. The presence of the blood in the sac acts as a stimulus to 
provoke its contraction, so that the blood never remains in it, but is 
returned up the duct as fast as it is received. This is all the more 
likely to be the case in that the duct of the crop is in line with the 
pharynx, while the part of the oesophagus leading to the proventriculus 
is bent at an angle. The straight course for the blood is into the crop. 

The term ' sucking stomach ', frequently applied to this structure both 
in this and in other flies is a misnomer, for whatever its function may be 
it certainly does nothing to assist in sucking up the blood, neither is it a 
stomach, in the sense of having any digestive action. The term oesopha- 
geal diverticulum is also undesirable, as hiding the essential similarity of 
this structure with that in other insects. 

The proventriculus is a long flattened tube, extending from the thoracic 

inlet to the commencement of the abdomen. In its anterior two-thirds it 

is about twice as broad in the transverse diameter as it 
Proventriculus ... . , , . , 

IS m the vertical, so that its lumen is a transverse slit, 

but posterior to this it becomes rounder, with a small circular lumen, and 
also much narrower. At the anterior end there are two broad lateral 
expansions, the anterior and external angles of which project forwards 
and receive minute nerves from the head. This part, when seen from 
the dorsal aspect, resembles a butterfly with expanded wings. With the 
exception of the posterior and rounded part the whole of the surface of 
the organ is studded with small regularly arranged elevations, which give 
it a mammilated appearance when examined under a low power ; there 
are four rows of such elevations on each of the dorsal and ventral 
surfaces, and two rows on each lateral border. 

The opening by which the oesophagus communicates with the pro- 
ventriculus is situated in a small elevation on the dorsal surface, not at 
the extreme end, but a little behind it. 

The minute structure of the wall of the proventriculus is essentially 
the same as that of the oesophagus, but the appearance on section is pro- 
foundly modified by the great increase in the thickness of the wall and the 
bunching up of the cells to form the elevations referred to above. A section 
through the middle of the tube shows a transverse lumen, with many 
narrow fissures passing into the substance of the wall on all sides. The 
lumen is bounded by a continuous sheet of finely granular material, 



PLATE XXI 



Figure 1. The alimentary canal of Tuba/iiis. ph., pharynx. 

oes., oesophagus, pv., proventriculus. d.c, duct of 
the crop, cr., crop, m.g., mid-gut. il., ileum, co. , 
colon, mp.t., Malpighian tubes, rt., rectum. X 25. 

Figure 2. Transverse section through the mid-gut of Tabamis, 
showing the villi, t.m., circular muscle fibres, l.m., 
longitudinal fibres, tr., trachea. X 60. 

Figure 3. Cells of the proventriculus of same, between two of the 
elevations in its wall, to show the external layer 
of eosinophil material. X 500. 

Figure 4. A section through one of the mamilhe of the proven- 
triculus of same, showing the continuation into them 
of the lumen, surrounded by the eosinophile layer. 
The line of sepai^ation between the cells is very indis- 
tinct in this region, mu., one of the irregular muscle 
fibres in the wall, x 500. 

Figure 5. A villus from the mid-gut of Tabamis. X 250. 

Figure 6. A transverse section through the proventriculus of 
same, about the level marked x in figure 1. X 150. 



PLATE.XXr. 




TABANUS: THE PROVENTRICULUS 105 



staining well with eosin and faintly or not at all with haematoxylin, which 
passes into all the fissures. (Plate XXI, fig. 4.) Internal to this there is 
a single layer of columnar cells, which are very indistinctly separated 
from one another, and are in many parts heaped together without any dis- 
tinguishable cell membrane. The nuclei are oval or rounded, and lie 
near the intima. The protoplasm is finely granular, and stains uni- 
formly, though not well, with iron haematoxylin and similar stains ; 
there is a narrow area just underneath the intima which stains more 
deeply than the rest. External to these cells there is. a rather thick base- 
ment membrane. 

The muscular coat of the proventriculus is well developed, and con- 
sists of a large number of coarse fibres scattered all over the surface ; 
they are arranged in an irregular manner, and not in separate circular 
and longitudinal bundles as is usually the case. 

The mamillation of the surface is due to the heaping up of cells 
around the fissures, and it is especially in these elevated areas that the 
cell membranes are difficult to define. Each elevation consists of a 
mass of protoplasm with numerous scattered nuclei, with a central 
area of finely granular eosinophile material, in the middle of which there 
is a fissure which represents the lumen, and is in continuity with the 
lumen of the rest of the tube. The expanded portions at the anterior end 
are almost entirely made up of such little masses, and present a very 
complex picture on section. The main portion of the lumen stops 
short at the point where the oesophagus and the duct of the crop enter 
the wall, and anterior to this there are only narrow fissures communi- 
cating with one another and with the rest of the lumen. 

The relations of the oesophagus, the crop, and the proventriculus 
are well brought out in a sagittal section. The lumen of the proven- 
triculus appears as a narrow slit, with numerous fissures radiating 
from it above and below ; the duct of the crop lies on the dorsal side 
of the proventriculus, and appears as a direct continuation of the 
oesophagus from the neck ; it communicates with the proventriculus by 
an opening on the dorsal side of the latter, some distance from the 
anterior end. 

At the posterior end the elevations become less marked, and the 
tube is reduced to one very similar to the oesophagus ; it merges 
gradually with the commencement of the mid-gut. 

The mid-gut is a large pear-shaped dilatation, with its narrowest end 
anterior. When it is empty the wall has a mamillated appearance like 
that of the proventriculus, but these markings disappear completely 
14 



106 



MEDICAL ENTOMOLOGY 



when the organ is distended with blood. It lies in the second and 

third segments of the abdomen, and is embedded in a dense coating of 

fat body. Next to the ovaries, it is the part of the 
Wlid-gut , , , 

body with the richest tracheal supply. 

The wall consists of a single layer of columnar epithelial cells, set 
on a basement membrane, and two layers of muscular fibres, an inner 
circular layer and an outer longitudinal one. 

The layer of columnar cells is collected into numerous villi, which 
project into the lumen on every side, giving it a stellate appearance. 
In the intervals between the villi the cells are regularly columnar, 
but those which compose the villus are altered in shape so as to 
adapt themselves to its contour ; the attached ends are narrowed and 
compressed together, while the part of the cell towards the lumen is 
correspondingly increased in size, its free border projecting into the 
lumen, and giving to the border of the villus a crenulated appearance. 
The basement membrane of the cells is tucked inwards at the base 
of the villus, and at this point a small trachea enters the wall and at 
once breaks up into minute branches. It is to the presence of these 
villi that the mid-gut owes its mamillated appearance. 

The cells of the mid-gut present very different appearances at different 
stages of the process of digestion, and comparatively little is kno\\'n 
about the changes which occur in them, in this or in any other blood- 
sucking fly, during the digestion of blood. In the resting condition, 
in which the fly is preparing for its meal of blood, the part of the 
cell anterior to the nucleus is filled up with vacuoles, of various sizes 
in different preparations ; they may be so minute as to impart only 
a granular appearance to the cell, or they may be so large as to break 
down the cell substance. The border of the cell is striated, and in 
many preparations appears to be ciliated, though it is doubtful if there 
are really free cilia present. The nucleus is large and oval, and is 
situated in the posterior part of the cell in those cells which lie 
between the villi, but near the lumen in the rest. At the base of many 
of the cells a second small and deeply staining nucleus can be dis- 
tinguished ; this represents an immature cell which will eventually grow 
to replace a degenerated one. 

The muscular coat of the mid-gut is of considerable thickness. The 
inner fibres are arranged a little obliquely, and interlace with one 
another. The outer longitudinal fibres are straighter, and are 
continuous with those of the hind-gut, the whole of the alimen- 
tary tract posterior to the proventriculus being enveloped in the same 



TABANUS: THE HIND-GUT 



107 



continuous sheet. At the lower end of the mid-gut, immediately above 
the attachment of the Malpighian tubes, there is a small dilatation, 
specially well provided with circular fibres, which act as a sphincter 
muscle. 

The hind-gut of Tahanus is naturally separated into two parts, 

an upper which is narrow and convoluted, and a lower which is 

wider and straight. The former, which may be termed ... ^ ^ 

... 1 Hind-gut 

the ileum, passes downwards and to the right, then 

transversely upwards and to the left; the wider part, or the^co/on, com- 
mences at the last turn, and from this point the gut passes directly 
backwards to the posterior end of the abdomen. The wall of the hind- 
gut (Plate XXn, fig. 5) consists of a single layer of regular cubical 
cells on a basement membrane, an inner layer of circular or oblique 
muscle fibres, and an outer layer of longitudinal ones ; neither of these 
are very well developed. The layer of chitin which is present on the 
internal aspect of the cells is much thicker in the posterior part of 
the canal than in the ileum, and can only be distinguished with difficulty 
in the part near the mid-gut. 

The colon is separated from the rectum by a short constriction. 
The rectum is typically pear-shaped, and opens between the last pair 
of dorsal and ventral plates by a narrow neck. Its wall has the same 
structure as that of the rest of the hind-gut, but the circular muscle 
fibres are much more strongly developed, and the internal chitinous 
layer is more conspicuous. In the wall of the rectum there are six rectal 
papillae or glands ; these are stout, curved, wedge-shaped bodies, each 
a little shorter in its long diameter than the rectum itself. They are 
inserted into the wall with their broad ends directed outwards, and 
project a little from the outer surface through the muscular coat; their 
pointed ends are directed towards the anus. Each consists of a mass 
of large cells arranged in a radiating manner around a central lumen 
which opens into the body cavity, and into which there passes a small 
tracheal twig. The papillae occupy a considerable proportion of the 
total area of the lumen of this part of the gut. Their function is un- 
known, but they are believed to be homologous with similar structures, 
of common occurrence in aquatic larvae, which function as respiratory 
organs by absorbing air from water. In many such larvae the papillae 
can be protruded from the rectum at will. 

In the hind-gut, from the ileum downwards, it is common to find, 
- in this and other blood-sucking flies, a number of coarse granules of 
a reddish colour. These are the residue from the last meal of blood. 



108 



MEDICAL ENTOMOLOGY 



They are very hard and gritty, and frequently spoil sections of this 
part of the gut. 

The Malpighian tubes differ somewhat in appearance in the different 

genera, but all conform to a general type, of which Tahaniis may be 

. . . taken as an example. There are four of these struc- 

Malpighian Tubes , . . , , . , 

tures, openmg at the junction between the mid-gut and 

the hind-gut. They are blind tubes of great length, at least twice 
as long as the body of the fly when dissected out. They lie in the abdom- 
inal cavity, and are coiled and twisted around the other organs in 
every direction, some appearing to pass into the posterior end of the 
thorax. The terminations of one pair are found near the anterior end of 
the mid-gut, and those of the other closely intertwined with tracheae 
and embedded in the fat body at the sides of the rectum. The tubes are 
of practically uniform diameter throughout, but are narrowed a little at 
the distal end. The wall is composed of large flattened cells, which are 
wrapped round the lumen and fitted to one another so as to form a com- 
plete tube ; as a result of this arrangement only one nucleus at most 
is cut in cross-section. (Plate XXII, figs. 1 and 2.) The tubes are well 
supplied with tracheae, and are so bound down by means of them that 
it is difficult to dissect them out entire. In stained preparations the 
nuclei are very conspicuous on account of their size and of the uniformity 
with which they take up the ordinary stains, no discrete particles 
of chromatin being distinguishable. In addition to the nuclei of the 
cells of the tubules there are a few other smaller ones, which belong 
to the ultimate divisions of the tracheae distal to the terminations 
of the spiral thread. These are, of course, distributed all over the tissues 
of the insect, but are only distinguishable in situations such as this, 
where they are not mixed up with other cells. 

The Malpighian tubules are probably excretory organs, which collect 
the waste products from the blood and fat body and pass them into 
the lumen of the intestine, from which they are passed out with the 
residue from the food. Their situation in many insects forms a useful 
landmark, but it must not be supposed that the manner in which 
they separate the mid-gut from the hind-gut is more than what one might 
perhaps term an accident. In many insects they open into the intestine 
much further down, as for instance in the bugs, where the opening 
is just above the anus. 

The alimentary canal of Tabanus will serve as a type for the rest 
of the blood-sucking Orthorrapha, with the exception of the Culicinae, 
which show many peculiarities, and will be dealt with separately. With 



PLATE. XXtt. 




Plate xxn 



Figure 1. Apiece of Malpighian tube from Tabaiiiis, showing 
the way the cells are wrapped round the lumen, x 100. 

Figure 2. Malpighian' tubes of same in section. Only one 
nucleus at most appears in an ordinary thin section. 

Figure 3. The alimentary canal of C;(//co/(/es /c;t;//(jr/. The crop 
IS not shown, m.g., mid-gut. mp.t., Malpighian 
tubes. CO., colon, rt., rectum. X yo. 

Figure 4. The alimentary canal of Phlebotonius iiiiiiutits. oes., 
oesophagus, d.c, duct of the crop, lying on it. cr., 
crop. Other letters as before. The dissection from 
which this was drawn was stretched a little, x 180. 

Figure 5. Cells from the wall of the hind-gut of Tabaniis. ch., 
the chitinous inner lamina. t.m., circular muscle, 
l.m., longitudinal muscle. X 800. 

Figure 6. A section through the upper part of the rectum of 
Tabamis. The section was a little oblique, and shows 
the whole of one rectal papilla, and a part of another, 
tr., trachea, mu., muscle, ch., chitinous lamina in 
the wall. In the lower part of the section this lamina is 
of considerable thickness, x 70. 

Figure 7. Section through the oesophagus of C/Jc;.v, anterior end. 

showing the chitinous spicules which project into the 
interior, and the absence of cells in the wall. 

Figure 8. Section through the same, lower down, in the thorax- 
Note the low cubical cells in the wall, and the large 
amount of muscle externally. The chitinous lamina 
is here not so well marked. 



ALIMENTARY TRACT OF MOSQUITO 



109 



the exception of Phlebotoinus, they have not been studied very closely, 

but so far as our knowledge goes they conform generally to the type 

seen in Tabaniis. The proventriculus does not ap- 

,, 1 , . . . . Other Orthorraphic 

pear to be so well developed in any of them as it is ^y^^^ 

in the latter, the oesophagus passing downwards as 
a simple tube to merge with the mid-gut. The digestive epithelium 
commences some distance anterior to the dilated part which is evid- 
ently mid-gut. The Malpighian tubules vary in their number and 
mode of origin. In Ciilicoides (Plate XXII, fig. 3) there is only one 
pair, but these are very thick, and are very conspicuous in dissections 
on account of their dead white colour, which is quite different to that of 
the hind-gut. In Simiiliuin there are two pairs which arise from a very 
short common stem, and in Phlebotoinus (Plate XXII, fig. 4) two pairs 
arising from a much longer common portion ; of the two on each 
side one is considerably longer than the other ; both terminate in slightly 
swollen ends. 

The crop is very well developed in Phlebotoinus ; its duct, which is 
an extremely fine one, leaves the oesophagus a little in front of the 
nape of the neck (Newstead). In Culicoides and Simulium it is 
not quite so large, but in none of them is it so closely connected with 
the oesophagus as it is in the Culicinae. It appears to function in 
a slightly different way to that of Tabanus, for both in Phlebotoinus 
and in Culicoides it is found distended with blood in flies killed 
immediately after feeding, while a few hours later it is empty or nearly 
so. Apparently the blood is received into it from the pharynx, and 
passed on to the mid-gut gradually, as fast as it can be digested. 
The mid-gut, like that of Tabanus, is capable of very great distension. 

The alimentary canal of the mosquito, like the rest of its anatomy, 
presents considerable modifications from the other Orthorrapha. 
The differences in the various genera, however, are not important, and 
for practical purposes all may be included in one description. 

The oesophagus is a short and thin-walled tube which passes from the 

posterior end of the pharynx in the head to the anterior part of the 

thorax, where it joins the mid-gut. The two are 

^ J , , , , , , . , The Mosquito— 

separated, however, by a valvular structure believed to Oesophagus 

be the homologue of the proventriculus. The wall is 
composed mainly of a single layer of flattened epithelial cells, with in- 
determinate boundaries and small oval deeply staining nuclei. Internal 
to this there is a thin chitinous intima, most marked in the anterior 
portion of the tube, where it is provided with a set of fine spicules 



ilo 



MEDICAL ENTOMOLOGY 



projecting into the lumen. The cells are more regular and conspicuous 
in the posterior part of the tube, where the intima is thinner. There 
is a thin layer of muscle fibres externally, best developed at the posterior 
end. The lumen of the tube may appear wide in sections, when the 
cells are very much flattened, or it may be contracted, in which case 
the cells are more cubical. Evidently the tube is capable of consider- 
able dilatation. 

The crop is of a totally different form to that of the other flies 

referred to, and consists of three sacs with excessively thin walls, termed 

the oesophageal diverticula. Two of these open into 
Crop or Diverticula , i 

the oesophagus on the dorso-lateral aspect, and one on 

the ventral side. Their shape is extremely variable, as they have no 
rigidity of their own, and are simply adapted to the structures among 
which they lie. When they are dissected out of the body they contract 
to form irregular ovoids. Usually they are filled up with minute bubbles 
of gas, but in newly-hatched mosquitoes they are collapsed. The two 
dorsal sacs are small, and do not extend beyond the thorax as a rule, but 
the ventral one is very large, and passes into the abdomen, even as far as 
the fifth segment, and occupies a very large proportion of the abdominal 
cavity. 

The wall of the sac consists of an extremely delicate chitinous intima 
in which a few scattered nuclei can be made out, and an external coating 
of extremely fine muscle fibres, which run transversely around the sac, 
but do not completely encircle it. The nature of the wall is best 
made out in sections of newly-hatched mosquitoes, in which the sacs 
have not been distended with air or blood. 

The function of these diverticula is the same as that of the crop in 
Tabaniis, with this difference, that in the mosquito the blood is retained 
rather longer in them. They are, in fact, true ' food reservoirs ', as was 
pointed out by Nuttall and Shipley. In mosquitoes killed during the act 
of feeding they are always found to be full of blood, while a little later, 
depending on the rate of digestion and therefore on the temperature, the 
blood is almost entirely confined to the mid-gut. The great distension of 
the body of a mosquito as it completes its meal is not due solely to the 
distension of the mid-gut, but also to the distension of the diverticula 
of the oesophagus. 

Nuttall and Shipley record some interesting observations with refer- 
ence to the function of these sacs. They fed mosquitoes on a mixture 
of blood serum and sugar, tinted with carmine, and again in twenty- 
four hours on the same mixture without the colour. On dissection, 




Ill 



PLATE XXni 



Figure 1. The alimentary tract of Citlex, dissected out without 
traction, l.d., lateral diverticulum, cd., cardia. St., 
' stomach ' : the cardia and the stomach make up the 
mid-gut. Other letters as before, x 80. 

Figure 2. Cells from the mid-gut of Culex. Note the internal 
layer, and the vacuoles, n., nuclei lying between the 
bases of the columnar cells. These belong to small 
cells which will eventually replace the columnar ones 
when desquamated. X 800. 

Figure 3. The mid-gut of Culex when distended with blood. 

The amount of distension m^ay be judged by compar- 
ing the relative size of the oesophagus in this figure 
and in figure 1. x 30. 

Figure 4. The shape of the mid- gut when dissected out by the 
ordinary method, involving traction. 

Figure 5. Schematic longitudinal section through the commence- 
ment of the mid-gut. s.a., opening of the diverticula, 
m.c, sphincter muscle separating the fore-gut and 
the mid-gut. c, chitinous intima. st., striated border 
(Stabchenschaum). m., external muscular fibres, 
ep., epithelium. After Schaudinn. 



MOSQUITO : THE MID-GUT 



111 



' the contents of the ventral sac were coloured red, that of the stom- 
ach yellow, so that there could be no doubt but that the second meal 
had been almost entirely taken up by the stomach'. They also confirmed 
this by the examination of living insects similarly fed, the coloured 
contents being plainly visible through the abdominal wall. Such an 
observation might, as they point out, have an important bearing on the 
development of any parasite taken up with the blood, but the fact must 
not be lost sight of that the conditions of the experiment were highly 
artificial, and it does not follow that the same result would be obtained 
if the experiment could be repeated with blood for both feeds. As a 
matter of fact mosquitoes under natural conditions will not, as a rule, 
feed till the last meal is completely digested, and in cold weather one fre- 
quently finds that an interval of as much as four days is necessary. 

The oesophageal valve, the supposed homologue of the proventriculus, 
is an invagination of the posterior end of the oesophagus into the com- 
mencement of the mid-gut. It forms a marked annular 

... Oesophageal Valve 
thickening due partly to a great mcrease m the circular 

muscles at this point, and partly to the presence, as pointed out by 
Nuttall and Shipley, of small protuberances, varying apparently in 
number in different species, which represent the caecal appendages of the 
larval insect. When examined in section (Plate XXIII, fig. 5) the valve 
is seen to consist of a double fold of the total thickness of the wall of the 
oesophagus, which is tucked inside the lumen of the commencement of 
the mid-gut. The circular muscles which surround the canal at this point 
presumably act in regulating the rate of passage of the blood from the 
diverticula to the digestive chamber. No such valve is found in Tabaniis, 
in which the blood is passed on at once into the gut, and is not stored 
in the crop. 

The mid-gut consists of two portions, which probably differ in their 
physiology as well as in their anatomy. The first part is tubular, and 
lies for the most part of its length in the thorax, and is ^.^ 
continued downwards from the oesophageal valve in 
continuity with the oesophagus. It is a rather thick tube of uniform 
diameter, and is marked at its anterior end by the thickening due to the 
valve and the caeca. This portion is termed by Thompson the cardia. 
At the outlet from the thorax, or a little behind this, it dilates to form 
an oval chamber about three times the breadth of the thoracic portion. 
This is the ' stomach ', and it is here that the blood accumulates 
during the process of digestion ; it is here also that the parasite 
of malaria is most frequently found. It terminates about the fifth segment 



112 



MEDICAL ENTOMOLOGY 



of the abdomen, and is separated from the hind-gut by a constriction at 
the point marked by the insertion of the Malpighian tubes. 

The shape of the mid-gut of the mosquito is very markedly affected by 
the method in which it is dissected out of the body. In the ordinary 
routine method, in which it is pulled through the posterior end of the 
abdomen by traction applied with a needle, and by rupturing the tracheae, 
the sharp distinction between the cardia and the ' stomach ' is lost by 
the rupture of some of the tissues of the wall, and although it resumes its 
shape to a certain extent when the traction ceases, it never assumes the 
shape it has when in sitil. The whole organ is elongated, the anterior 
part especially, and is correspondingly reduced in its transverse 
diameter ; it then assumes the flask-shape so familiar in drawings of the 
organ. To get a correct view it is necessarj^ to dissect away the body 
wall piecemeal, without pulling on the gut at all (Plate XXIII, 
figs. 3 and 4). 

The wall of the mid-gut, both in the cardia and the dilated portion, 
consists of a single layer of epithelium. This is of the same type as that 
in Tabanus, but is much shorter ; the cells are cubical rather than 
columnar, and are distributed in an even manner without villi. The bor- 
ders of the cells are distinctly striated, and internal to the striations there 
is a more darkly staining area. Coarse granules and vacuoles are usually 
present, and the rest of the protoplasm shows fine granulations. There 
is little difference to be observed between the cells in the narrow 
part and those in the dilated portion, except that those of the latter are 
higher. As in Tabanus, the cells become flattened when the gut is 
filled with blood. 

External to the cells and their basement membrane there is a layer 
of circular muscle fibres, and external to this some scattered longitu- 
dinal ones. The circular fibres are well marked at the lower end of 
the gut, where they form a sphincter which separates the mid-gut from 
the hind-gut. 

The hind-gut resembles that of Tabanus so closely that there is 
no need for a detailed description. The Malpighian tubes possess 
but one peculiarity, that in Culex there are five of them instead of four. 

The alimentary canal in the Cyclorrapha is much more complex 
and highly organized than in the Orthorrapha. In the first place, 

its length is very greatly increased, while at the same 
Alimentary Canal in ^. j i , j i- j.u 

the Cyclorrapha time there is no dilated portion representing the 

mid-gut as seen in Tabanus and in the mosquitoes. 

The effect of this increase in length and diminution in diameter must 



ALIMENTARY TRACT OF PHILAEMATOMYIA 113 



obviously be an advantageous one, for it exposes a larger surface of 
digestive cells, and at the same time reduces the distance by which 
the central particles of food are separated from the gut wall. The 
increase in length, which is confined to the mid-gut, has necessarily 
resulted in throwing the tube into many convolutions. The proven - 
triculus has assumed a definite shape common to all, and forms a 
valve separating the fore-gut from the mid-gut. 

The most striking development is the formation of a second tube 
internal to the epithelium, by which the food contained in the gut 
is separated from the digestive cells. This structure is known as the 
pentrophic membrane. It is found in many other insects, and also in 
their larvae, and indeed it is somewhat remarkable that it should be 
absent in the Orthorraphic flies. 

The form of the alimentary canal in the Cyclorraphic Diptera 
is remarkably constant in the different genera, such differences as there 
are being mainly in the length of the tube and the complexity of the 
coils. That of Philaematomyia will serve as a type ; the parts in 
some other members of the group will be referred to subsequently. 

The oesophagus is a short tube which passes through the neck from the 

posterior end of the pharynx to the anterior part of the thorax. At its 

commencement it is of considerable width, but it very 

^ ^ r ^ 1 V - u Philaematomyia— 

soon contracts to form a narrow tube which passes Oesophagus 

through the brain and neck. The structure of the 

wall is the same as that of Tahamis, except that there is rather more 

muscular tissue. 

As it passes into the thorax the oesophagus lies ventral to the pro- 
ventriculus, and comes into close contact with it. The two communicate 
by an opening which is directed upwards and slightly backwards ; 
immediately posterior to this point the duct of the crop commences, and 
runs backwards into the abdomen ventral to the gut. The oesophagus 
and the duct of the crop appear in fact to form a continuous tube, 
closely pressed against the proventriculus; the communication between 
it and the proventriculus is only revealed by sections. 

The crop is a large and thin-walled sac like that of Tabanits, 

situated in the anterior portion of the abdomen. When empty 

it is contracted, but when the fly has iust finished 

... Crop 
feedmg it is distended with blood, and may occupy 

a considerable proportion of the abdominal cavity. Its wall is thicker 

than that of the corresponding organ in the Orthorraphic flies, both 

the muscular and cellular portions being more conspicuous. 

15 



114 



MEDICAL ENTOMOLOGY 



It will be noted that the positions of the crop and the proventriculus 
are the reverse of those in Tabanus, a fact which throws some light 
on the development of the parts. It seems probable that in some remote 
ancestor the crop was a simple dilatation of the oesophagus, such as is 
found in many modern insects, and that this dilatation became divided into 
several portions, one or more of which passed backwards towards the 
abdomen, remaining connected with the oesophagus only by a narrow 
duct. In Tabanus the crop has developed from a dorsal sacculation, 
in the Muscidae from a ventral one. In the mosquito the develop- 
ment is seen at an early stage, in which three of the original sacculations 
are present, one of them, the ventral, being predominant, and extend- 
ing to the abdomen when distended. All these structures function in 
the same way, receiving the blood from the pharynx and passing it on 
to the mid-gut for digestion, but the rate at which the crop is emptied 
seems to differ in the different forms. In some, as in Tabanus, the 
contractions of the crop appear to be as rapid as those of the pharynx, 
so that the blood is passed on to the gut at once, while in others, among 
which are Musca and Philaematomyia, the food is retained for a time, 
and passed on gradually. The object of the crop is to enable the fly 
to absorb a very large amount of food at one time — ^evidently a great 
advantage in the case of those flies which do not remain permanently 
in association with the host on whose blood they feed. 

The proventriculus is a small disc-shaped body, flattened from 
above downwards, but placed rather obliquely in the thorax, with its lower 

edge directed downwards and forwards. The dorsal 
Proventriculus . . i r • 

surface is smooth and convex ; the ventral surface is 

irregular on account of the attachment of the oesophagus and the duct 
of the crop. 

The structure of the proventriculus is best understood from the 
study of a longitudinal section, such as that shown in Plate XXIV, 
fig. 2. It consists of a mass of cells, part of which are derived from 
the mid-gut and part from the fore-gut. The external layer is continuous 
with the mid-gut and is composed of columnar cells which are longest 
in the anterior portion. Inside this there is a thick plug of smaller round 
cells which belong to the fore-gut. The oesophagus is, in fact, tucked 
inside the dilated end of the mid-gut, the portion which is invaginated 
having a greatly thickened wall. The opening by which the oesophagus 
and the mid-gut communicate lies in the middle of this plug, and is 
not shown in the section figured, as this is not precisely through the 
middle line. The invaginated portion is button-shaped, and, since the 



MUSCIDAE: THE MID-GUT 



115 



mid-gut is attached to it at some distance from its periphery and on the 
anterior side, there is an annular recess between the edges of the plug 
and the anterior end of the cells belonging to the mid-gut. It is in this 
recess that the peritrophic membrane arises. 

The structural arrangements at the communication of the oesophagus 
with the mid-gut are evidently adapted to function as a valve to prevent 
regurgitation of the contents of the gut. Pressure of fluid in the 
anterior end of the mid-gut would result in dilatation of the annular 
recess, and would, therefore, compress the sides of the opening of the 
oesophagus. A sphincter muscle has been described in this region 
in Miisca. Its presence would not appear to be necessary for the 
efficient working of the valve. 

The mid -gut is an elongated tube, extending from the proventriculus in 
the thorax to the distal portion of the abdomen. It is many times the 

length of the cavity in which it lies, and is thrown into 

•, J • J ■ J ■ J Mid-gut 

many coils and twisted upon itseli in order to accom- 
modate its shape to the space available. It is to the length of the mid-gut 
that the elongation of the alimentary tract is due, for the fore-gut and 
hind-gut are relatively no longer than those in the Orthorraphic flies. The 
coils in Philaematotnyia are closely similar to those in Stoinoxys. The 
separate turns are held loosely in position by the tracheae which supply 
them with air. 

The mid-gut may be conveniently divided into three portions. The 
first of these is a narrow tube immediately posterior to the proven- 
triculus, which passes directl)' through the thorax without convolutions. 
This expands after a short course to form the portion known as the 
ventriciihis, or chylific ventricle, which is the widest part of the gut ; it 
lies in the posterior part of the thorax and in the abdomen, and is twisted 
into a double coil in its posterior part. The third part, corresponding to 
rather less than half the total length of the mid-gut, is known as the 
proximal intestine, a rather unfortunate term ; it should not be confused 
with the hind-gut. It is about half the diameter of the ventriculus, and 
is more loosely coiled. At its posterior end the Malpighian tubes enter 
the gut. 

The wall of the mid-gut is lined throughout with a digestive epithelium 
similar in its general appearance to that of Tahanus. The cells are 
arranged in a single layer, and vary in height, the largest cells being 
found in the ventriculus. Those lining the narrow anterior portion of 
the gut are regularly cubical (Plate XXV, fig. 3). In the ventriculus, and 
to a lesser extent in the proximal intestine, the wall is iu many places 



116 



MEDICAL ENTOMOLOGY 



raised into small protuberances, between which there are shallow fossae. 
In many sections one linds the cells undergoing changes connected with 
the process of digestion, and discharging their contents into the lumen. 
(Plate XXV, fig. 4.) 

External to the cells there are circular and longitudinal muscle fibres, 
both of which are well developed. 

The hind -gut is similar to that of Tabanus, and is of about the same 
length in proportion to the size of the fly. It is of uniform diameter, 
H'nd ut ^ slight constriction about its middle point, 

where the circular muscle fibres are strongly devel- 
oped so as to form a sphincter. At the distal end it opens into a rectum 
like that of the Orthorraphic flies, with four rectal papillae. 

The structure of the wall of the hind-gut is simple. There is a single 
layer of regular cubical cells, with a chitinous intima which is best devel- 
oped in the posterior portion, and external to this the usual two layers of 
muscle, of which the circular fibres are the most strongly developed. 
The chitinous intima in the lower part is developed into a series of 
short spines, which project into the lumen of the gut, and are directed 
towards the anus. (Plate XXIV, fig. 3.) 

The Malpighian tubes arise on each side by a common stem, and 

pass forward and backward among the tissues. Like those of Tabanus 

they are composed of a single layer of cells, but the 
Malpighian tubes ... . 

individual cells are rounder, and their central portions 

project a little from the surface, thus giving to the tube a wavy 
contour. At the distal end, for about one-quarter the length of the tube, 
the lumen is dilated and filled with a densely white granular material, 
which stretches the cells composing the wall and distorts the regular ar- 
rangement found in the lower portions. The dilatation is most irregu- 
lar, so much so that this part of the tubule appears to consist of a 
series of elongated pouches connected together by narrow necks. The 
wall is here very fragile and easily ruptured. The degree to which the 
tube is distended and filled with this white material varies in different 
specimens, and probably depends on the age of the fly. 

The peritrophic membrane (Plate XXIV, figs. 4 and 5), already referred 
to, forms an inner tube which extends from the proventriculus to the 
Peritrophic mem- anus, and completely separates the contents of the gut 
brane from the epithelium. It hangs down from the pro- 

ventriculus, in fact, like a tubular curtain, and is in contact with the cells 
at all points but nowhere attached to them except at its upper end. It is 
composed of an extremely thin and translucent material which is very 



PLATE XXIV 



Figure 1. The alimentary tract of Philaetnatomyia insignis. 

C.V., chylific ventricle, or first part of the mid-gut. 
p.i., proximal intestine, pv., proventriculus. sp., a 
thickening of the circular muscle of the gut -wall, 
probably acting as a sphincter, h.g., hind-gut. Other 
letters as before, x 12. 

Figure 2. A longitudinal section through the proventriculus of 
Philaeinatomyia insignis, showing the origin of the 
peritrophic membrane, j., the junction of the fore gut 
and the mid-gut. oes., the invagination of the 
oesophagus into the mid-gut. f.g., fore-gut. c, com- 
mencement of the mid-gut. pt.m., peritrophic 
membrane. 

Figure 3. Cells from the hind-gut of Philaeinatomyia insignis, 
showing the chitinous spines. 

Figure 4. A diagrammatic section through the mid-gut of a Muscid 
fly to show the peritrophic membrane ifi situ, m.c, 
the cavity of the mesenteron. ep., epithelium of 
digestive cells, pt.m., peritrophic membrane. 

Figure 5. A diagrammatic longitudinal section of the alimentary 
tract of a Muscid fly, to show the relations of the 
peritrophic membrane. Lettering as before. This 
and the last figure after Berlese, slightly modified. 

Figure 6. A portion of the distal end of the Malpighian tube of 
Philaematoniyia insignis. X 150. 

Figure 7. A portion of the proximal end of the same. X 150. 

Figure 8. The alimentary tract of Glossina, in sitii. ph., 
pharynx. oes., oesophagus, c.cg., the common 
salivary duct, formed by the union of the two ducts, 
c.j., duct of the crop, j., the crop, pr., proventriculus. 
i.th., thoracic portion of the intestine, i.m., abdominal 
portion, a.r., rectal ampulla, gl.s., salivary glands, 
r., rectum, or hind-gut. p.r., rectal papillae. From 
Rouband, after Minchin. 



GLOSSINA: THE MID-GUT 



117 



delicate and easily ruptured, but which possesses sufficient coherence to 
enable one, by careful dissection, to draw out a considerable portion of it 
intact and containing the food. 

The significance of this membrane will be evident from its relations. 
It is a continuous sheet with no apertures, and therefore the digestive 
fluids from the cells, and the digested products from the food, must 
pass through it as through an osmotic membrane. 

The peritrophic membrane, according to Berlese, is composed of 
chitin, secreted by special cells situated at the junction of the proven- 
triculus with the mid-gut, to which is added a deposit of mucous sub- 
stance secreted by the cells of the mesenteron. It appears to grow 
downwards from the mesenteron till it reaches the anus. 

The alimentary canal of Miisca is very similar to that of PJiilaematomyia. 
The mid-gut is a little longer and more convoluted, and the ventriculus 
broader. The latter is narrower at its anterior end 

Musca 

than elsewhere, but it is not separated from the pro- 
ventriculus by a definite neck as is the case in Philaematomyia, so that 
almost the whole of the part lies in the thorax. The Malpighian tubes 
are not usually dilated at the ends and are often of a yellowish or 
greenish colour. It is rather remarkable that the colour of the tubes 
should differ in different species. 

It should be noted that the part of the gut sometimes referred to 
as the * distal intestine' is the hind-gut. The proximal intestine belongs 
to the mid-gut or mesenteron. 

The alimentary canal of Stomoxys is like that of Philaematomyia , and 

is of about the same length. The narrow portion anterior to the dilated 

ventriculus is longer, and extends through the thorax. 

^1 ■ • • r 1- r 1 • 11 1 1 1 1 Stomoxys 

This IS, m tact, a peculiarity lound in all the blood- 
sucking Muscids which have been examined, and is probably related to 
their habit of taking in a large meal at one time. The Malpighian tubes 
show an interesting feature, first pointed out by Tulloch in the 
case of Stomoxys, but probably of common occurrence, namely, that 
the dilated distal ends of one pair pass to the dorsal region and lie 
in a constant position near the heart and pericardial cells. As these 
two tubules arise by a common stem, it is possible, as suggested by 
Minchin, that the tubes should be regarded as dorsal and ventral, not as 
lateral. 

In Glossina there is a great elongation of the mid-gut, which has 
brought about a corresponding complexity in the coils into which it is 
thrown. The proventriculus, according to Minchin, is saddle-shaped, 



118 



MEDICAL ENTOMOLOGY 



that is to say, concave longitudinally and convex transversely when 
seen from above. Its lateral portions are wrapped round the oesophagus 
Glossina ^^'^ <iuct of the crop, which therefore appear to 
be embedded in the substance of the organ. The crop 
is relatively large, and is always found to be full of fresh blood when the 
fly has had a full meal. When the fly has not fed recently the crop con- 
tains bubbles of gas. 

In all these flies it is the anterior portion of the mid-gut, or the 
ventriculus, in which the fresh blood is found after feeding. The nar- 
rower portion posterior to this, which, following the usual nomenclature, 
has been termed the proximal intestine, frequently contains a darker 
and more viscid material composed of partially digested blood. 

In Hippobosca and Melophagtis the alimentary tract presents a strik- 
ing peculiarity in the absence of a crop, a condition of affairs which is 

correlated to their method of feeding. Hihbobosca 
Hippobosca P11 • If • 1 1 1 1 1 T 

does not nil itself with blood at one puncture, but flits 

about from place to place on the skin of the host, remaining with it for 
long periods. Indeed, it is rare to find a fly of this genus apart from 
its host, which it does not leave even for copulation. Melophagtis, 
which is wingless, cannot leave the host at all during the active 
period of its life, but is associated with it after the manner of the fleas. 
In neither case is there any necessity for the fly to take a large meal, and 
consequently there is no necessity for a crop. 

The proventriculus in Hippobosca is represented by a small oval 
swelling on the anterior portion of the gut. The mid-gut is very long 
and is twisted into many coils, and has the same general character as that 
of Musca. The anterior portion is mych thicker than the rest, though 
the gut as a whole is wider than that of any of the other flies referred 
to. The rectum is large and capacious, and generally contains a milky 
fluid. Its wall is thick and leathery, and of a dark brown colour, quite 
unlike that of Musca. 

There are four Malpighian tubes, which arise independently from the 
gut. They are simple and of a uniform diameter, and have not the bead- 
like appearance of those in the Muscidae, and are distinctly narrower. 
The hind-gut posterior to their origin is slightly swollen ; it contracts 
again at the point where it joins the rectum. 

In the foregoing the term ' hind-gut ' has been used in the sense in 
which it is ordinarily understood, as that part of the alimentary tract 
posterior to the openings of the Malpighian tubes. The actual extent of 
the posterior invagination, which is lined by a chitinous intima, is not as 



PLATE XXV 



Figure 1. The hind-gut of Hippobosca maculata, showing the 
openings of the four separate Malpighian tubes and 
the rectal ampulla, v., sphincter muscle at the opening 
into the ampulla, d.i., distal intestine, mp.t., Malpi- 
ghian tubes. X 36. 

FigLure 2. A transverse section through the posterior part of the 
abdomen of Haeiitatopota pliivialis. The section from 
which this was drawn was not cut in an absolutely 
transverse plane, so that the two sides are not symme- 
trical, t.m., circular muscle fibres, connecting the 
tergite and sternite. f.b., fat body, j.m., longitudinal 
muscle fibres, connecting the adjacent tergites and 
sternites respectively, h., heart and pericardial cells, 
h.g., hind-gut, cut in three places on account of its 
twist. ov., ovaries : the several tubules are cut at 
different levels, some through the nurse cells, the nuclei 
of which are conspicuous. a.g., accessory glands of 
the reproductive organs, x 66. 

Figure 3. Cells from the upper part of the mid-gut of Philae- 
Diatouiyia insigiiis, a short distance below the pro- 
ventriculus. x 500. 

Figure 4. Cells from the middle portion of the mid-gut of the 
same, x 450. 

Figure 5. Longitudinal section through the abdomen of Philae- 
matomyia insigiiis, to one side of the middle line, 
ha., haematocoele, always apparently a large space in 
sections, on account of the unavoidable shrinkage, d.i., 
portions of the distal intestine cut through obliquely, 
ch.t., abdominal tergite. r.p., rectal papilla, rt., 
rectum, c, a mass of cells around the rectum, most 
of which belong to the proximal ends of the Malpi- 
ghian tubes, mb., the membraneous portion of the 
ventral wall, which is only chitinized in the middle line, 
p.i., proximal intestine, sl.g., salivary glands, ch.v., 
chylific ventricle, m.ph., mesophragma. pv., proven- 
triculus. Note the large number of circular muscle 
bundles, x 69. 

Figure 6. The rectum of Miisca, showing the tracheae entering 
the rectal papilla?, x 6$. 



PLATE. XXV. 



t.m. f.t). l.ni. h. mp.t. i.m. h.g. pv. 




f 

j 

I 



THE SALIVARY APPARATUS 



119 



yet definitely ascertained for the various Muscidae. It could only be 
found by a very carefully prepared series of sections of the whole of the 
hind part of the tract. The appearance seen in a recently fed fly 
suggests that the extent of the digestive portion is actually less than 
the terms used indicate. 

The salivary apparatus consists of glands situated in the thorax, 
extending in some cases to the abdomen, ducts to convey the fluid 
from them through the neck, a reservoir or valve 
situated in the head, and an efferent duct along which ^Apparatus' 
the saliva flows into the wound. The distal part 
of the apparatus has already been described in connection with the 
mouth parts. The thoracic salivary glands in the Diptera correspond to 
the lingual glands in other insects. The labial glands are present only 
in Musca and its near allies, and in Tabanus ; they have been described 
as they occur in Musca, and need not be further referred to here, except 
to remark that their existence should not be forgotten when considering 
the possible modes of exit of a parasite from the body of a fly. 

Regarding the nature and use of the saliva we have little information. 

It has been frequently stated, with little evidence, that its purpose 

is to prevent the coagulation of the blood during 

. . Function of saliva 

its transit from the host to the alimentary tract of the 

fly. It has also been suggested that the effect of the secretion, by produc- 
ing the familiar inflammatory phenomena, is of value to the insect in 
that it facilitates the flow of blood. It has been shown by Nuttall 
and Shipley that the salivary glands of Culex, when emulsified, pos- 
sess neither the power of haemolizing the blood in the mid-gut, or 
of preventing clotting. In the case of Tabanus the blood corpuscles 
are intact and apparently uninjured up to at least seven minutes after 
feeding. 

All the Diptera which habitually suck the blood of man undoubtedly 
have in their saliva some substance which produces a painful inflam- 
mation, and it is remarkable how different individuals react to this 
substance. With the mosquito, people living under identical circum- 
stances will exhibit widely different degrees of reaction, judged both by 
the visible effects and by the amount of irritation induced. Some degree 
of immunity appears to be established after a time, and the person, though 
bitten as frequently as before, sufl'ers much less from the individual 
bites, many of which he barely notices. The fact that an old inhab- 
itant suffers less from insect bites than a new arrival in the tropics 
is much more likely to be accounted for by the lesser degree 



120 



MEDICAL ENTOMOLOGY 



of reaction than by any actual dimunition in the number of bites 
inflicted. 

A similar idiosyncrasy is to be noticed with regard to other insects. 
Many people suffer acutely from the bites of Tabanids, which in 
the majority of cases produce only a momentary irritation and some 
rubifaction. The same thing has been noticed with Simiiliiim. 

The salivary glands of the Diptera are usually tubular and elongate, 

though great variation in their length is met with in the order. The 

^. . blind end is often a little dilated, giving it a saccular 
The Glands , , , , • • 

appearance, and possibly enablmg it to retain a quan- 
tity of saliva. The glands may extend through the thorax, and be 
twisted into many convolutions on account of their length, or they 
may be confined to the anterior part of the thorax. The increase 
in the length of the glands corresponds with other anatomical points 
which indicate a high degree of specialization. For instance, in 
Phlehotomiis they are short and round, while in Glossina they are 
extremely long. The increase in length gives, of course, a greater 
extent of secreting surface, as was pointed out in connection with 
the alimentary canal. 

The salivary glands of mosquitoes are of particular importance 
since it is in them, in certain species of Anopheles, that the parasite 

of malaria is to be found previous to its entrance into 
Culex and Anopheles , , , , , ^, r , , i i 

the blood of man. They are oi the tubular type, and 

are confined to the thorax of the insect. Certain differences between the 
glands in Anopheles and Culex (Plate XXVII, figs. 7 and 8) have been 
emphasized by Christophers and by Nuttall and Shipley. 

There are three glands on each side, lying in the lower part of the 
anterior end of the thorax, immediately above the first pair of legs. 
They are just below the main mass of thoracic muscle, and lie embedded 
in fat body. The ducts meet in a common point as they emerge from 
the substance of each gland, and lead by a common duct to the neck, 
where those of the two sides unite in the region of the occiput, and 
under the sub-oesophageal ganglion, to form a single channel, which 
passes to the salivary pump described in connection with the mouth 
parts. 

Each acinus is an elongate tubule, within which, in the fresh state, the 
intra-acinar duct can be seen. Of the three acini on each side the one 
which lies between the others, and appears dorsal to them in cross sec- 
tions of the anterior part of the thorax, is slightly smaller than its fellows. 
All the glands consist of a single row of cubical or short columnar cells 



THE SALIVARY APPARATUS 



121 



arranged around a central lumen, which is constituted by the intra-acinar 
duct. Outside the cells there is a well-defined basement membrane. At 
times small secondary acini or bifurcations of one or other of the three 
glands are met with. 

The lateral glands, which are of what Christophers terms the ' granu- 
lar ' type, are generally almost filled with a granular secretion, which 
compresses the protoplasm and the nucleus of the cell towards the outer 
border. In the fresh condition the secretion is clear and refractile, 
while in sections it appears as a coarse reticulum, due, as pointed out by 
Christophers, to a precipitation of the secretion by the fixative. It does 
not stain with eosin, and only faintly with haematoxylin. There is some 
reason to believe that the portion of the gland adjacent to the junction 
of the three ducts is different to the rest, for Grassi notes that its secre- 
tion is more refractile, while Christophers states that the cells in this 
situation are smaller, and the lumen of the gland correspondingly 
restricted. In some species of Ctilex the reverse is the case, the cells 
in this region being cylindrical ; there is, however, a good deal of differ- 
ence in different species and individuals in the appearance of the 
glands. 

The central glands are of what Christophers terms of the ' colloid ' 
type. The cells are not so much compressed, and contain more pro- 
toplasm than those of the lateral glands. Unlike that of the latter, 
the secretion stains well with eosin and also with haematoxylin ; it is 
less refractile in the fresh condition. 

The appearance of the intra-acinar duct differs a little in Ctilex and 
Anopheles. In the former it is of the same width throughout, and 
terminates near the blind end of the gland, while in Anopheles it termi- 
nates in an indefinite manner about the middle, so that the upper 
portion of the gland is expanded and forms a reservoir for the storage 
of saliva. The main ducts give off a few small lateral branches, which 
end blindly. Under a high magnification minute pores can be seen in 
the chitinous wall of the ducts. 

Little or no change takes place in the glands as a result of feeding ; 
it is probable that only a small amount of saliva is passed down at each 
bite, and that it is very rapidly replaced by the secreting cells. 

In newly hatched and unfed mosquitoes the cells of the gland are much 
more regular, and the nucleus is little if at all compressed by the 
secretion. In this condition the nucleus stains very deeply and is 
placed centrally. The protoplasm distal to the nucleus contains many 
very fine granules and one or two vacuoles. 
16 



122 



MEDICAL ENTOMOLOGY 



The salivary glands of Phlebotomtis, as described by Newstead, lie 
in a position corresponding to those of the mosquito. There is only 
one pair of glands at each side. They are pear-shaped structures, 
composed of a single layer of remarkably large cells surrounding a 
central lumen. 

In the Tabanidae (Plate XXVII, fig. 9), the glands are long and tubular, 

and extend into the anterior part of the abdomen. They lie in the 

lower part of the thorax slightly below and on either 
Tabanus . . 

side of the proventriculus for the most of their length, 

and turn outwards a little at their distal ends, which are somewhat dilated. 

The lumen of the glands contains a fine granular eosinophile material 

when seen in stained sections. The wall is composed of a single layer 

of cubical or short columnar cells, with well defined nuclei, which are 

never compressed like those in the salivary glands of mosquitoes. The 

chromatin of the nuclei is divided up into a number of sharply separated 

particles. The cells have a well defined basement membrane, which 

is well demonstrated when fresh specimens are ruptured. 

In the Muscidae the glands are always long, and extend into the 

abdomen; they may, as in Glossiiia (Plate XXIV, fig. 8), be much coiled. 

They are recognized at once on opening the abdomen 
Muscidae ... ... 

by their glistening white colour, which is quite unlike 

that of the gut or the Malpighian tubes. They are attached to the 

surrounding organs by many tracheal twigs, and cannot be drawn out 

through the neck without rupturing unless they are first freed from their 

attachments. 

The only differences in the different genera are in the length. Glossina 
appears to have the longest, though those of Philaematoinyia are 
also very long. Stoinoxys has rather short glands, shorter than those 
of Musca. The glands are so similar in structure to those of Tabanus 
as to call for no further description. 

The relationship of the salivary glands to the surrounding structures 
should be noted. They lie, as do the other organs, free in the haema- 
tocoele, and are bathed by the blood. Those flies which have long 
glands extending into the abdomen have also long and coiled alimentary 
tracts, so that the wall of the gut and the wall of the glands are in 
contact at many points, as can be readily shown by sections. Should 
any parasite, motile or otherwise, pierce the wall of the gut and thus 
become free in the haematocoele, there is therefore every chance that 
it may also pierce the wall of the gland. No special selective faculty 
on the part of the parasite need be assumed. 



ASSIMILATION OF FOOD 



121 



DIGESTION AND ABSORPTION 

Our knowledge regarding the nature and mechanism of the processes 
by which food material ingested by the insect is converted into assimi- 
lable substances and used up in nutrition is unfortunately very scanty. 
Packard, writing fifteen years ago, devoted only six pages to the subject, 
while Berlese's recent voluminous work contains little more. Neither 
entomologists or parasitologists have given special attention to the case 
of the digestion of blood, and even Schaudinn, who recognized the 
importance of the matter, touched on it only incidentally, without giving 
any account of the histological appearances. It must be remembered, 
however, that the changing conditions met with in the alimentary tract 
during digestion constitute the environment of ingested parasites, and 
have therefore a special importance from the present point of view. 
The following account is by no means as full as the importance of the 
subject demands. 

The part of the alimentary tract which is specially concerned with 

digestion and absorption is the mid-gut, or mesenteron, which is equipped 

for this purpose with a secreting epithelium, the cells 

r 1 • 1 1 • • Function of 

of which are usually columnar and have no chitmous mesenteron 

intima. The secretion is passed out into the lumen of 
the gut, where it mixes with the food, resolving it into soluble sub- 
stances, which are then taken up by the cells and passed into the body 
cavity. Phagocytosis of food particles does not take place. The fore- 
gut, derived from the stomodaeum, serves as a channel to pass the food 
from the mouth to the digestive chamber, and is modified in various 
ways, as has already been pointed out, to regulate the flow, and in certain 
cases to act as a food reservoir. In many mandibulate insects, such as 
the cockroach, the part of the fore-gut immediately anterior to the 
mid-gut is dilated to form a chamber termed the crop, into which open cer- 
tain gland-like organs, the caeca. In this chamber a preliminary diges- 
tion takes place, the inlet into the mid-gut being meanwhile shut off by a 
strong sphincter muscle. In blood-sucking insects, however, digestion is 
confined entirely to the mid-gut, and the crop serves at most as a 
temporary reservoir for the food. Instead of appearing only as a simple 

dilatation of the oesophagus, it may be separated from 

, , , Digestion in the 

it by a long duct, the receptacle itself being situated in ^^^^ 

the abdomen. As will be shown presently, the 

cells of the posterior part of the stomodaeum have also the function of 

providing a covering layer for the fluid food on its entry into the mid-gut. 



MEDICAL ENTOMOLOGY 



The posterior portion of the tract, derived from the proctodaeum, 
serves only to conduct the residue resulting from the digestive process, 
and the secretion of the Malpighian or urinary tubules, to the 
exterior. 

■ The salivary glands probably provide some secretion which is con- 
cerned in digestion, directly or indirectly. Little is known regarding its 

„ ..- . . exact properties or function, but one thing is evident 
Salivary glands . , . , , • i i 

from anatomical considerations, namely, that in blood- 
sucking insects it is necessary for the saliva to be conveyed to the 
wound. The salivary system does not come into communication with 
the alimentary tract anywhere except at the prestomum. In the 
Diptera the conveyance of the saliva is arranged for by the elongation 
of the hypopharynx ; in the Hemiptera and Siphonaptera, as will be 
explained in later chapters, the same end is attained by different means. 

It has been stated that solid particles are not ingested by the cells of 
the mid-gut, that is, that the food substances are rendered soluble before 
they are absorbed. The proof of this lies in the 

Significance of presence of the peritrophic membrane, which has 
the peritrophic . . 

membrane already been described as it occurs in the alimentary 

tract of Philaematoinyia. The presence of such a 
structure, completely separating the cells of the gut from the ingested 
particles, renders necessary the assumption that the soluble products 
of digestion arrive at the cells after passing through the membrane. 

In the Muscid flies, as in many other insects and their larvae, the 
peritrophic membrane is a well-defined structure, which possesses sufficient 
cohesion to enable one to separate it from the gut wall, and passes to 
the distal end of the tract. In the Orthorraphic flies, on the other hand 
(at least in Culex and Tabaniis, which have been carefully examined), no 
such definite membrane exists, there being only a delicate la3'er of 
homogenous tissue, which stains faintly with eosin, between the blood in 
the gut and the cells ; this layer is so fine that it can only be distin- 
guished under the most favourable conditions. According to Schaudinn, 
who noted its presence in the mosquito, it is formed as a secretion of the 
chitinogenous cells of the fore-gut, given off by them as the fly feeds, and 
passed into the mid-gut as a protecting envelope surrounding the mass of 
blood. But in these Orthorraphic flies the gut is a distensible organ, 
and is increased to many times its normal diameter when the insect has 
ingested a full meal, and the layer of secretion, only a thin one at the 
most, becomes so thinned out by the stretching of the wall that it can 
BO longer be recognized. It can, as was pointed out by Schaudinn, be 



i 



PLATE. XXVI 




Fig. 2. 



PLATE XXVI 



Figure 1. A villus of the mid-gut of Tabaniis, immediately after 
the first meal of blood. The deeper cells are highly 
vacuolated, while the ones nearer the lumen are dis- 
charging their contents into it, and are disintegrating. 

Figure 2. A section through the same gut, at a lower level, and 
nearer the centre. The dark area on the right of the 
drawing is blood pigment, derived from the digestion 
of the layer of blood which has been in contact with 
the epithelium. The rest of the lumen is filled up 
with disintegrating cells, loaded with granules. In 
some the nucleus, in varying stages of disintegration, 
persists. In others there are large vacuoles. In the 
spaces between the cells there is a quantity of granu- 
lar matter derived from the breaking down of cells. 



r 



DIGESTION : SECRETION 



125 



seen if the specimen is killed and fixed immediately after it has com- 
menced to feed, that is, before the gut becomes distended with blood. 
The first figure on Plate XXVI shows it in a specimen of Tabamis 
removed before the completion of its first meal after hatching and fixed 
at once. In the section from which this drawing was made there 
were many places around the periphery where the layer could not be 
distinguished. 

The process of secretion of digestive fluid by the cells of the mid-gut in 

blood-sucking flies is similar to that which has been described for solid 

feeders. Previous to and during digestion globules 

appear in the protoplasm between the nucleus and the Secretion and 
^\ r r excretion 

striated border, and gradually increase in size, the 

smaller ones coalescing to form large globules near the free border, till 
they distend the cell wall, causing it to bulge into the lumen of the gut. 
The striated border then gives way at a weak point, and a mass of 
globules is extruded. In many cases the orifice through which the 
globules pass is a narrow one, so that when the cell is killed in the act of 
getting rid of its contents, as in some of those in the figure, the mass is 
flask-shaped, and still remains attached to the cell by a narrow neck which 
passes through the aperture in the striated border, the remainder of the 
mass having rounded off as soon as it became free. In other cases 
the whole of the border seems to give way, and a shower of globules 
only loosely attached to one another is set free. During this process 
the cell itself alters in shape, probably on account of the state of tension 
which exists in its interior. The nucleus moves nearer to the lumen and 
the whole cell takes on a more conical shape ; it remains attached to the 
basal membrane by a long and narrow basal process, while the part 
towards the lumen is correspondingly swollen, and may project into 
the lumen beyond its fellows. 

In some cases, but not by any means in all, the globules take with 
them a part of the protoplasm of the cell, including the nucleus. When 
this occurs the nucleus is always in a condition of degeneration, as is 
evidenced by the readiness and diffuseness with which it stains, and the 
large irregular clumps into which its chromatin is collected. Such nuclei 
in all stages of degeneration can be found free in the lumen in sections 
of the gut, and can often be seen in the act of leaving the epithelium. 

In the Muscid flies one finds, in most sections, cells at all stages of 
this process, whether the gut is distended with blood or not ; a row of 
normal resting cells is seldom seen. The conditions found in the biting 
flies are approximately the same as in Miisca, although their feeding 



126 



MEDICAL ENTOMOLOGY 



habits are entirely different, as they take one large meal and then rest 
while digestion proceeds, while Musca and its allies feed intermittently. 
In the Orthorraphic flies, which characteristically take one large meal 
from the same wound, the process of excretion is seen only when the flies 
are caught in the act of sucking. When examined in the fasting state 
only globules of small size are found, and these do not cause any marked 
bulging of the cell. If examined after a full meal, before digestion 
has proceeded far, say within the first four or five hours, the cells 
are found to be flattened out by the distension of the gut and the 
stretching of the wall until they resemble a squamous epithelium ; 
the longest axis of the cells then lies in the direction of the circular 
muscle fibres. Even in Tabaniis, in which the cells are invaginated 
into the lumen in the form of villi in the resting condition, this is 
the case, as the first effect of the distension of the gut is to flatten 
the folds until the epithelium is disposed in a single layer of colum- 
nar cells ; later, with an increase in the contents of the gut, these 
become flattened, gaining in one diameter what they lose in the other. 
The discharge of the secretion into the lumen is, therefore, a sudden 
one, taking place under the stimulus of the entry of blood, and is 
complete within a very short time after the meal is ingested. Probably 
the great increase in tension in the gut and its wall materially assists 
in the process. 

The appearances seen in sections of the mid-gut during this process 
are to a large extent artificial. The digestive fluid contains substances 
which are precipitated by the alcohol used in the preparation of the 
tissues, and these appear in the section as granules, surrounding 
the clear spaces which represent the vacuoles. It is, of course, pos- 
sible that some of the granules seen are pre-existent in the cell. 

The action of the digestive fluid on the red blood cells results 

first in haemolysis, and subsequently in the formation of a brownish 

black pigment from the undigested residue. This 
Digestion of blood " ° .1, i i j 1 u <-u 

occurs wherever the blood corpuscles reach the 

periphery, and thus come into contact with the secretion as it is 
discharged from the cells. But the blood in the gut is kept in a 
state of constant movement by the contraction of the longitudinal 
and circular muscle fibres of the wall, so that the layer of haemolized 
cells and the resulting pigment are moved away as soon as they are 
formed, and their place taken by fresh cells, until the whole has 
been digested. In some parts of the gut from which the figures on 
Plate XXVI were drawn layers of pigment formed in this way can 



REGENERATION OF DIGESTIVE EPITHELIUM 127 



be seen still retaining the impress of the depressed villi against 

which they were formed. At a later stage the whole of the pigment 

is collected in the middle of the posterior part of the chamber, being 

driven there by the repeated contractions of the wall. * 

As the blood pigment increases in amount it is passed through 

the sphincter muscle into the hind-gut, where it mingles with the 

secretion of the Malpighian tubes. According to 

^ , , , , , ,• 1 • r Contents of hind-gut 

Schaudmn, the quantity oi the latter, which is oi a 

yellowish white colour, is increased as absorption of food from the 

mid-gut proceeds, and one should, therefore, be able to estimate the 

stage of digestion which exists in the gut from the colour of the 

faeces. The problem is complicated, however, by the fact that the hind-gut, 

like the mid-gut, is in a state of active peristalsis during digestion, 

as is shown by the frequently made observation that blood-sucking 

flies defaecate while feeding. The faeces first passed during the act 

of feeding consist of dark tarry-looking masses, which may be either 

the remains of the last meal, as is most probable, or freshly-formed 

pigment. Later fresh red blood is passed in many cases. In caught 

flies one almost always finds some granules of pigment in the hind-gut, 

in the form of small hard crystalline masses. 

As the contents of the gut are absorbed the cells lose their flattened 

shape ; they become first cubical, and later assume their ordinary columnar 

form as the wall contracts around the diminishing 

, r 1 1 1 ^1 1-11 , 11 Regeneration of cells 

volume OI blood. 1 hose which nave degenerated and 

passed out into the lumen are replaced by the growth of the small cells 
which are always to be found between the regular columnar cells, and 
at their bases, in the condition of the rest. These increase in size 
within a few hours of the feed. In one to three days, according to the 
species, the temperature, and the size of the meal ingested, the gut 
assumes its normal appearance, and globules destined to be discharged 
at the next meal accumulate within the cells. When, as in Tabanus, 
the cells are heaped up into villi, these appear at an early stage, while 
there is still plenty of blood in the gut. 

In the foregoing no account is given of the chemical aspects of the 
digestive process. The amount of information on this question is 
at present neither large enough nor sufficiently exact to be of 
practical use. 



* The corpuscles tend to accumulate at the posterior end of the mid-gut, and the serum 
at the anterior end, as a result of this peristalsis. 



128 



MEDICAL ENTOMOLOGY 



THE HEART, VESSELS, AND PERICARDIAL CELLS 

The circulation of the blood of insects plays apparently only a 
secondary part in their physiology. The heart is a longitudinal dorsal 
tube, situated in the middle line and closely pressed against the tergal 
plates ; it extends from the posterior part of the abdomen to the thorax, 
where it is replaced by a thinner vessel, the aorta, which passes through 
the thorax and neck, and divides into two lateral branches about the 
occipital foramen. The aorta and the head vessels are very hard to 
trace, and can as a rule only be found in the larger flies. The heart 
itself is best seen by dissecting off the whole of the dorsal wall of the 
abdomen in one piece, and then drawing two tergites apart in order to 
rupture the vessel. One end of it usually remains projecting from 
one of the fragments, and can be recognized under a low power by its 
pulsation. 

The heart is not a simple tube, but is divided into a number of small 

chambers, which correspond more or less with the abdominal segments. 

Between each two segments of the heart there is a 
The heart . i i i , r n • 

simple valve, which prevents the blood from flowing 

backwards when the walls of the chamber contract, and on each side of each 
segment there is an opening through which the heart is put in com- 
munication with the body cavity. There are no veins, and no arteries 
other than the forward prolongation of the heart referred to as the 
aorta. 

The wall of the heart consists of a fine elastic intima, an intermediate 
layer of loosely arranged cells, and a muscular layer, the fibres of 
which are arranged as a rule in an obliquely circular direction and inter- 
lace with one another ; outside these there is said to be a thin layer of 
fibrous tissue. The heart is separated from the rest of the body con- 
tents by a layer of muscle and membrane which constitutes a sort 
of diaphragm, (Plate XXVII, fig. 11.) On each side of the middle 
line there is a set of fine fan-shaped muscles, one pair to each tergite, 
which arise near the lateral borders and expand as they pass inwards ; 
they unite with one another across the middle line as a fine sheet of 
membrane, which lies immediately below the heart. The space between 
the membrane and the insect's heart is filled in with large cells, termed 
the pericardial cells, and there are apertures in the membrane below 
these, through which the pericardial chamber communicates with the 
rest of the body cavity. The heart and pericardial cells are well sup- 
plied with tracheae ; branches from ah the abdominal spiracles pass 



THE HEART AND HAEMATOCOELE 



129 



directly inwards across the dorsal wall, and unite with one another 
in the middle line below the diaphragm. 

The mechanism of the heart is as follows. When the muscular 
fibres in its wall contract, the openings by which the chambers com- 
municate with the body cavity are closed : as the 

, . r 1 Mechanism 

blood is compressed it passes forwards, retrogression 

being prevented by the valves which separate the chambers of the 
heart from one another. The heart is thus emptied into the aorta, 
and a forward flow of blood brought about. 

The heart muscle then relaxes, and at the same time the alar muscle 
contracts ; its contraction increases the space between the diaphragm and 
the dorsal wall, and causes the blood to enter the space through the 
apertures in the diaphragm, and thus to circulate among the pericardial 
cells in which the heart lies. Probably the muscles of the abdominal 
wall also assist by compressing the abdominal contents to a slight 
extent. Contraction of the heart then commences again, and in this 
way an intermittent stream of blood is kept flowing from behind 
forwards ; all the blood circulates among the pericardial cells as it 
passes from the abdomen to the heart. The pericardial cells are 
believed to have some special function in purifying the blood, but in 
view of the little that is known of insect metabolism it is idle to specu- 
late as to what this may be. 

The body cavity has already been mentioned in connection with the 
heart, as the space from which the blood is drawn into the contrac- 
tile chambers. It is worth a little more attention 

. , ... The Haematocoele 

than is usually paid to it by parasitologists, on ac- 
count of its relations to all the organs of the body, and especially to 
the proboscis. 

When an insect is opened up by removing the dorsal or ventral wall, 
the internal organs are seen lying free in a space bounded only by the 
exo-skeleton and the layer of cells immediately internal to it ; they 
have no attachments other than those formed by the tracheae. This 
space is the haematocoele. In the living insect it is filled up by 
the blood, which bathes all the internal structures and is kept 
moving by the action of the heart. The stream of blood passes 
forwards in the dorsal tube, and, leaving it at the termination 
of the aorta in the head, it returns to the abdomen in two lateral 
streams, which divide up into numerous streamlets as they pass among 
the contents of the cavity. Now the lumen of the alimentary tract is 
only separated from the blood in the haematocoele by the thickness 
17 



130 



MEDICAL ENTOMOLOGY 



of the wall, and this is neither very great nor is the wall in that part 
which lies in the thorax and abdomen of such a nature as would render 
it difficult of penetration by any parasite possessed of means of move- 
ment. Once a parasite has penetrated the wall of the alimentary 
canal and become free in the body cavity, then, whether it is motile or 
not, it will, unless it is too large to pass through the lateral openings 
into the heart, be drawn into the circulation and transported to the 
head ; it may then, of course, find its way back in the slower backward 
stream, or it may become attached or entangled in some part of the body. 

The relations of the haematocoele in the proboscis of the fly have 
been described at some length in connection with the mechanism of the 
mouth parts. If what was said on that subject be considered from the 
point of view of the possible movements of a parasite which has per- 
forated the wall of the alimentarj' tract, it will at once be obvious 
how intimate are the relations of the parasite to the blood in the 
wound, or to the food surface in the case of the non-biting flies. Once 
it is free in the blood of the abdomen it may be caught up at the dilata- 
tion of the heart, and on the next contraction it may be forced along with 
the blood stream into the aorta, and so on directly to the head. In the 
eversion and closure of the labella, which together constitute the act of 
biting in the Muscid flies, there is a forcible and rapid to-and-fro move- 
ment of the blood in the lower part of the proboscis, and the chances that 
the parasite will sooner or later be driven into the space between the 
inner and outer walls of the labella are very great indeed. When it has 
arrived there it is only separated from the blood of the presumptive 
vertebrate host by the thin inner wall of the labella. Whether and under 
what circumstances this inner wall could be perforated is one of the 
questions to be decided in each case. 

The relations of the haematocoele of the labella are the most striking 
in the case of Miisca and its biting allies, but the same conditions are to 
be found in the Orthorraphic biting flies. The labella of Tabaniis, when 
they function as feeding organs, are distended in exactly the same way as 
those of Mtisca, and the distension can be readily demonstrated experi- 
mentally by pressure on the head. In other forms, in which the labella 
are not functional in this manner, it is extremely probable that something 
of the same kind occurs in the eversion of the labella preliminary to 
the insertion of the piercing parts. In the mosquito the position of 
the tip of the proboscis, which appears to act merely as a guide and 
support to the other parts, is a most suggestive one. 

The blood is ea-sily obtained for examination by taking one of 



PLATE XXVII 



Figure 1. The nervous system of Tabaims. br., brain, a.n., 
anterinal nerve, o.l., optic lobe. n.t, nerve trunk, 
formed from two branches which emerge from the 
suboesophageal ganglion. t.g., thoracic ganglion, 
ab.g., abdominal ganglia. X 140. 

Figure 2. Pericardial cells from Haematopota. x 500. 

Figure 3. Fat body from a newly hatched Philaematoinyia. 

eo., compact homogeneous particles which stain 
brightly with eosin. v., vacuoles, n., nucleus. 

Figure 4. Tlie compound thoracic ganglion of Miisca doinestica. 
After Gordon Hewitt. 

Figure 5. Cross-section of the salivary gland of Haematopota. 
X 400. 

Figure 6. Longitudinal section through the salivary gland of 
Ciilex. sl.d., the salivary duct. X 800. 

Figure 7. The salivary gland of Culex fatigans. 

Figure 8. The salivary gland of Anopheles rossii. 

Figure 9. One salivary gland of Tabaiws alhimedins. X 30. 

Figure 10. Cells of the labial salivary gland of Haematopota. 

These are similar to those in Musca, and to those of 
Philaematoinyia, in which, however, the permanent 
vacuole is not so well seen, n., large nucleus, n'., 
small nucleus at the opposite end of the cell, v., 
vacuole. X 650. 

Figure 11. Scheme of the circulatory system. h., heart, p.c, 
pericardial cell, t., tergite. aim., alary muscle : the 
tendons spread out in the middle hne, and form a wide 
sheet perforated in places, ha., haematocoele. ov., 
ovaries, al.t., alimentary tract. st. sternite. The 
arrows indicate the direction of the flow of the blood, 
through the interstices between the fat body and the 
organs, into the pericardial chamber and the heart, 
within which it is propelled forwards through th^ 
aorta to the head. 




130 



THE FAT BODY 



131 



the larger flies, and, without other dissection, making a small nick 
in the membrane connecting two of the abdominal plates. A pipette 
with a fine bore is then inserted, and a considerable 

The blood 

quantity of a yellowish fluid obtained. Blood may also 
be obtained in small drops, but with more risk of contamination, by 
pulling off the legs and picking up the fluid as it escapes on a cover- 
slip ; or in the case of flies with a well-developed pseudotracheal 
membrane, by compressing the head until the blood is pressed into the 
labella, from which it can be withdrawn in a pipette, or smeared out by 
rupturing the labella on a slide. 

Blood so obtained is a rather viscid yellow fluid, containing an 
extremely small number of cells ; so poor is the fluid in cellular contents 
that several large smears may have to be examined before finding' a 
single cell, and those which are seen may be so fragmentary and indis- 
tinct as to be hardly recognizable as such. Many varieties of cells 
have been described from insect blood, but when special precautions 
are taken to avoid touching any of the internal organs one frequently 
finds no cells at all, or at most a few which might be the small hypodermal 
cells internal to the integument. The blood corpuscles, sometimes called 
leucocytes (the amehocetti of Berlese), are very small rounded or oval 
bodies, each containing a single nucleus and a reticulated cytoplasm. 
In many a definite nucleus is absent. 

On opening the abdomen of a recently-hatched insect all that is 

seen at first is a sheet of whitish tissue, with a greenish or bluish 

tinge, which envelopes all the organs. When this is split . . 

' ,. . . . , ^ The fat body 

up by dissection it is found to consist of a number of 

minute lobules connected together by thinner portions, which are drawn 

into threads as they are pulled on by the needle. This is the so-called fat 

body, really a mass of only slightly differentiated mesoblastic tissue, the 

walls, if such they may be called, of the haematocoele. It envelopes all the 

internal organs, and is always found in considerable quantity around 

the digestive part of the alimentary tract ; a thinner sheet of it forms 

an inner coating to the internal surface of the body wall ; between 

these two layers, and in all the interstices between the lobules and 

the cells of which the tissue is composed, the blood of the fly passes 

as it circulates to-and-fro in the body. The cells of the fat body 

are large, and when closely packed together are moulded to one another 

so as to present a mosaic pattern on section ; in newly-hatched flies 

they contain a nucleus and a finely-reticulated protoplasm, and are 

loaded with globules of fat (Plate XXVII, fig. 3). 



132 



MEDICAL ENTOMOLOGY 



The exact function of the fat body is not known, but it is evidently 
an important one closely connected with the metabolism of the fly, 
for it has a rich supply of tracheae. The quantity present in newly- 
hatched flies and in fully-fed larvae is much greater than that found 
in older specimens, and the appearance of the cells is greatly altered 
concurrently with the diminution in amount. The cells lose their 
nuclei, the protoplasm becomes broken up and replaced by large vacuoles, 
and sometimes crystals may be found in them. Most probably the fat 
body is a store of reserve food material accumulated in the larval 
stage, to assist the insect in the reproductive phase ; there is also some 
reason to believe that it assists in the elimination from the body of waste 
products. 

THE REPRODUCTIVE SYSTEM 

The organs of reproduction are situated in the posterior part of the 
abdomen between the alimentary tract and the ventral chain of nerve 
ganglia. The external opening lies anterior and ventral to the anus, 
from which it is separated by the sternal plate of the last segment. 
The separate elements of which the system is composed are paired and 
situated laterally, only the posterior efferent duct and the opening to the 
exterior being common to the two sides. The genital opening is sur- 
rounded by certain modified parts of the exo-skeleton, forming the exter- 
nal genitalia already described, the purpose of which is to assist in 
copulation, and, in the female, in oviposition. The sexes are always 
complete and distinct from one another in the Diptera. The internal 
organs of reproduction of the male exhibit a wide degree of variation, 
as is the case with the external parts. 

The essential sexual elements are certain cells derived from the 

blastoderm, which are contained in the male testes and in the female 

ovaries. Leading from these organs there are ducts to 
General structure ... 

convey the sexual products to the exterior, known as the 

vasa defereiitia and the oviducts respectively ; in the course of these ducts 
there may be dilatations or diverticula for the reception of the sperms, 
prior to copulation in the male, and after copulation in the female. 
The posterior portions of these ducts are fused with one another, and are 
formed, together with a portion of the bilateral ducts, by an invagination 
of the cuticle ; they are therefore lined with chitin continuous with that 
of the exo-skeleton. The chitin may be present in a dense and pigmented 
layer in certain parts, as in the spermathecae of mosquitoes. In association 



MALE ORGANS OF REPRODUCTION 133 



with the S5'stem there are usually certain glands of a mucous nature and 

of considerable size ; those of the female are designed to provide the 

ova with a superficial covering, by which they are in many cases 

attached either to one another or to some stationary object. The 

external opening of the male tract is at the end of a chitinous penis; 

that of the female is a dilatable chamber with a muscular wall. The 

fused portion of the female tract may become very highly developed in 

the pupiparous forms, in which it contains the larva during the period of 

its growth and development. 

Much yet remains to be investigated regarding the relations of the 

sexes in the Diptera. It has been said that the spermathecae, or the 

dilatations on the efferent duct of the tract in the female, ^ . . 

, 1 • 1 r 1 1 ^1 Relations of sexes 

contam the spermatozoa derived from the male. The 

female, once having received a supply, can go on developing her ova in 
several batches, without being dependent, so far as is known, on a second 
copulation. But it is not known with certainty at what period of the 
growth of the ova fertilization takes place, or how soon after emergence 
from the pupal state the two sexes meet. There appears to be some relation 
between the time at which the first feed is taken and the time at which 
copulation occurs, which may perhaps account for the extraordinary diffi- 
culty which is sometimes met with in persuading newly-hatched flies to 
feed. There also remains to be explained the well-known difference 
which is found in the proportions of the two sexes. When breeding 
mosquitoes, for instance, a large majority of those which emerge are 
males, while on the contrary there are some species of Tahanus and 
Haematopota of which the female is a common fly, and the male ex- 
tremely rare. The difference in numbers in the latter case is far too great 
to be accounted for by the more obtrusive habits of the female. The 
conditions suggest that the male, once having copulated and fulfilled 
its purpose in the propagation of the race, dies off, leaving the female to 
live as long as she has eggs to lay. The point may possibly have a 
practical interest in cases in which both sexes are blood-suckers. 

The male organs are confined to the posterior portion of the abdomen, 
and are only of interest here in that the observer ^ ^ 
should be able to recognize them when met with 
during dissection. 

In the mosquito (Plate XXVIII, fig. 3) the testes are small ovoid bodies, 
with a slightly green tinge in the fresh state. The vasa deferentia which 
lead from them are extremely slender tubes of con- 

Culex and Tabanus 

siderable length ; each expands at the distal end to 



134 



MEDICAL ENTOMOLOGY 



form a small receptacle, from which a short common ejaculatory duct 

passes to the genital opening. On each side there is a globular accessory 

gland closely pressed against the seminal receptacle. In Tabanus (fig. 1) 

the testes are similar but a little longer, and have much shorter vasa 

deferentia, which open into a seminal receptacle of considerable size ; the 

receptacle is pear-shaped, and receives the vasae at its broad anterior end ; 

it opens below by an ejaculatory duct into the chitinous penis. It 

has much muscular tissue in its wall, and presumably plays an active 

part in expelling the seminal fluid in copulation. 

In Phlebotomus, the parts of which have been described by Newstead 

and Grassi, the testes are small oval organs of variable outline, which lead 

by short ducts to a pear-shaped seminal vesicle, which 
Phlebotomus , , • , ■ , , ' , . 

m turn is produced mto a short ejaculatory duct. This 

leads to an interesting apparatus termed by Grassi the ' pompetta '; 
this consists of a hollow cylindrical chamber containing a piston-like 
rod, which is provided with muscles by means of which it can be moved up 
and down ; as the opening of the ejaculatory duct is near the lower end 
of the chamber, the action of the rod will be, according to Grassi, to 
regulate the exit of the seminal fluid after the manner of a pump. 

In Musca and its allies (fig. 4) the testes are recognized at once by 
their brown colour. They are small pyriform bodies, leading by a 
short and narrow vas deferens to a stouter common 

Musca 

duct, which may be regarded as the vesicula seminalis. 

Its lower end is contracted to form a short ejaculatory duct. There are 

no accessory glands. 

In Glossina the reproductive organs of the male are different to those 

of the rest of the Muscidae, and resemble rather the type found in the 

Pupipara. The testes are simple tubes of a brownish 
Glossina . 

colour and are twisted on themselves in many coils. The 

testicular tube is continued downwards to become continuous with a vas 
deferens of slightly greater calibre. These unite in the middle line to 
form a common ejaculatory duct. There is a pair of accessory glands, 
twisted on themselves like the testes, but distinguished from them by 
their white colour and by the fact that they do not terminate in a fine 
point as do the latter. These open at the point of fusion of the vasae to 
form the ejaculatory duct. 

In Hippobosca (fig. 4) the testes are simple tubes of very great length, 
and are twisted on themselves to form a compact mass like a ball of string. 

The terminal portion is a little wider than the rest, and 
Hippobosca usually to be seen on the outer side, slightly separat- 



PLATE XXVIII 



Figure 1. The genital organs of Tabatnis, S . X 20. 

Figure 2. The genital organs of Miisca, S . 

Figure 3. The genital organs of Ciilex, S . X 50. 

Figure 4. The genital organs of Hippobosca, S , They resemble 
those of Glossina. x 90. 

Reference letters 

t. testes. 

v.d. vasa deferentia. 

c.d. the common ejaculatory duct. 

v.s. vesicula seminalis. 

a.g. accessory glands. 

p. penis. 

p.s. sheath of the penis. 

t'. in figure 4, the terminal portion of the testicular tube. 



PLATEJQM. 




FEMALE ORGANS OF REPRODUCTION 135 



ed from the coil. The lowest coil of the tube is continuous with the vas 
deferens, which is also twisted, but more loosely. The two vasae meet 
in the middle line, as in Glossina, to form a common ejaculatory duct, 
which is of much thinner calibre. Both the vasae and the testicles are 
of a rich brown colour. There is a pair of accessory glands, not coil- 
ed, but dilated and bent at the upper end, which open at the junction 
of the vasae of the two sides. These accessory glands are of a glistening 
white colour in the fresh state. There are two pairs of such glands in 
Melophagiis. 

The reproductive organs of the female are of special interest in 
connection with the hereditary transmission of parasites. 

Reproduction among the Diptera takes place, in the majority of 

instances, by the deposition of eggs and a complete metamorphosis. 

In some, however, the development from egg to larva . . ^ 

The Femsle Or^sns 

takes place in the body of the female, and the larva is 

produced either when still young and active or when it is ready for 

pupation. The oviparous forms will be discussed first. 

The essential organs of the female are the ovaries, each of which 
consists of a number of ovarian tubes, or ovarioles. The ovarioles open 
into an ovarian duct on each side, the ducts of the two sides uniting to 
form a common channel. This in turn leads into a short cavity known 
as the bursa copulatrix, which opens at the genital opening. The 
spermathecae, or receptacles for the sperms from the male, and the 
accessory glands, open into the common oviduct. It is the common 
oviduct which is modified to form a receptacle for the larva when it 
passes through the whole or a part of its development in the body 
of the parent. 

The ovaries are rounded or pear-shaped bodies possessing little 

cohesion or definite shape. The separate tubes of which they are 

composed are only very loosely attached to one 

1 1 r 1 11 Ovaries 

another, the mvestment oi the whole organ consistmg 

of a few scattered muscular fibres continued upwards from the 
oviduct. Each ovarian tube terminates as a fine filament at the upper 
end, and the filaments from each tube in the ovary are collected 
together to form a sort of suspensory ligament, which passes upwards 
and forwards, and can be traced to the fat body in the region of the 
heart. This is known as the apical filament. 

The size and shape of the ovaries depend entirely on the condition of 
the eggs which are developing in them. When the batch of eggs to be 
laid next is approaching maturity, the ovaries are very large, and may 



136 



MEDICAL ENTOMOLOGY 



compress all the other abdominal contents into the anterior and dorsal 
portion of the cavity, at the same time distending the abdominal wall 
and stretching the membrane which unites the dorsal and ventral plates. 
The mature ovaries of the mosquito appear as conspicuous white bodies, 
easily seen through the ventral and lateral walls of the abdomen. In 
newly-hatched females, on the other hand, the ovaries are very small 
and inconspicuous. 

Each ovarian tube is divided into a number of chambers or follicles, 
each of which produces one egg. There are usually four or five follicles 
to be seen in each tube, and these show a progressively advanced stage of 
development from the apical filament downwards, the uppermost one 
consisting only of a small collection of undifferentiated cells, while the 
lowest follicle contains a well developed ovum. When one batch of 
eggs is laid the next lowest follicle comes to maturity and takes its 
place, and so on in rotation during the life of the fly. 

The structure of the follicles is best explained by following the 

development from its early stages. In the newly-hatched fly they 

are very small and delicate structures, consisting only 
Structure of follicles . > b j 

of a number of large cells at the upper end of the 

ovarian tube. Out of this mass three different parts arise. The 
central cells enlarge, and one of them, the future ovum, passes to 
the lower part of the mass ; the rest, which are to become the nurse 
cells whose duty it is to nourish the ovum, pass to the upper pole. 
The remainder become changed into a layer of regular cubical cells, 
which form a covering for the ovum and its nurse cells. A number 
of cells from the original mass remain at the upper pole, outside 
the epithelial layer. The ovum and the nurse cells now begin to 
show marked alterations. The nurse cells become greatly enlarged, 
and have very large nuclei, while the ovum accumulates around its 
nucleus a quantity of granular material, which, gradually increasing in 
amount, forces the nurse cells still further towards the upper pole, 
until the ovum comes to occupy the greater part of the space in the 
follicle. The epithelium remains as a complete layer covering the 
whole. The granular food material of the ovum soon obscures the 
nucleus, so that it can no longer be made out in fresh preparations. 
When the egg is ripe the epithelial layer forms a part of its covering, 
while the nurse cells disappear entirely. 

While this is going on the small mass of cells left outside the 
first follicle also commences to undergo a similar series of changes, 
but as it starts after the first follicle it is always smaller. It in turn 



PLATE.XXDC. 




137 



PLATE XXIX 



Figure 1. An ovarian tube from Stomoxys. x 50. 

Figure 2. An ovarian tube from Culex. x 350. 

Figure 3. The common oviduct and connected structures of 
Musca. 

Figure 4. Spermathecae of Haematopota. x 3i. 

Figure 5. The reproductive organs of Haematopota. x 12. 

Figure 6. Spermatozoon from Musca nebula. 

Reference letters 

ap. apical filament. 

2, 3, 4 undeveloped follicles. 

n. nurse cells. 

ov. ovum. 

ep. epithelial layer. 

sp. spermathecse. 

a.g. accessory glands. 

c.d. common ovarian duct. 

ov.d. oviduct. 

e.g. conglobate gland. 

c. mass of undifferentiated cells, m which separate foll- 
icles cannot be distinguished (germarium). 



FEMALE ORGANS OF REPRODUCTION 137 



has a small cap of undifferentiated cells at its upper pole, which goes 
to form the third follicle, and so on, the succeeding follicles being pro- 
gressively smaller in accordance with their age. In the mature ovariole 
there is, therefore, one fully developed egg ready to be laid, and several 
follicles at various stages of growth. - 

The above account will apply to the Diptera generally. Individual 
differences are found in the relative degrees of development at which it 
is usual to find the different series of eggs, and this affects the 
shape of the ovarian tube as a whole. In the mosquitoes the first 
follicle becomes nearly mature before the development in the second is 
much advanced, and while the third and fourth are little more than 
masses of undifferentiated cells ; when the apical filament is broken and 
the tube rendered flaccid these undeveloped follicles appear as a little 
cap on the upper pole of the nearly mature egg. In the Muscidae 
the follicles after the first are more advanced, so that an isolated tube 
appears longer. Tahanus occupies an intermediate position. In each 
case, however, the appearance is accentuated by the shape of the egg ; 
that of Culex (Plate XXIX, fig. 2) is almost round, while that of 
Stomoxys (fig. 1) is a long ovoid. 

The paired oviducts and the common oviduct have muscular walls 
with well developed transverse fibres, which doubtless aid in the ex- 
pulsion of the ova. They are lined internally with 

. . . Oviducts 

a layer of flat cells with small nuclei, superficial to 

which there is a delicate lamina of chitin continuous with that of the 
integument. The bursa copulatrix is not as well developed in the 
Diptera as it is in some other orders of insects, and is not easily 
distinguished. In Haematopota it is provided with a series of minute 
spines set on a chitinous framework, which apparently engage with 
the male organs in copulation. 

The other parts of the reproductive system show considerable vari- 
ations in the different genera. The spermathecae are small chambers 

with chitinous and pigmented walls, formed as in- 

. SpermathecaB 

vaginations of the wall of the oviduct, and having, 

therefore, a layer of small cells external to the thick chitinous wall. 
In Anopheles there is only one such sac, with a long and narrow duct. 
In Culex and Stegomyia there are three. In Tahanus and Haematopota 
(fig. 4) the spermathecae are long fine tubes, bent on themselves in the 
middle of their length ; the slightly expanded blind ends are attached 
to the wall of the oviduct near the origin of the tube. The chitin 
forming the internal laj'er of the wall is thickest near the blind end, 
18 



138 



MEDICAL ENTOMOLOGY 



and is transversely striated. At the base of each tube, where it joins 

the oviduct, there is a peculiar funnel-shaped collar of thick chitin, 

surrounded by a series of spiral filaments like the rings of a trachea. 

The whole tube has a distinct coating of muscle fibres. In Phlehotomns 

there are only two spermathecae, one on each side of the middle 

line at the junction of the oviducts. They are relatively large and 

thin walled, but at the point where the duct leaves them the wall is 

thicker, and is thrown into transverse ridges. In Miisca (fig. 3) 

there are three spermathecae resembling those of the mosquito, but 

flattened at the top, and without a continuous chitinous wall. 

The accessory glands differ in size. In Anopheles they are very 

small, and open near the lower end of the oviduct. In Tabanus (fig. 

5) they are large, and are conspicuous in dissections on 
Accessory glands . , ,, , c ^ 

account oi the dirty yellow colour of the secretion 

which they contain. The wall is composed of columnar epithelial 
cells with many muscular fibres, and is thrown into longitudinal folds. 
In Phlehotomns also there is a pair of long tubular glands. In Musca 
(fig. 3) there are two pairs, one long and thin, and another, the so- 
called conglobate gland, rounded or pear-shaped ; the latter is situated 
close to the wall of the oviduct, and is often difficult to see on that 
account. 

The pupiparous habit occurs in three distinct degrees in the Diptera. 
In many Tachinids, which are not blood-suckers, the larvae are de- 
livered almost as soon as they hatch out of the egg, 

The Reproductive g^j.g ^gj-y small. They undergo little or no develop- 

**''^parous*Flies"''' i^^^it in the uterus, and are laid in a large batch, exactly 
as eggs are laid. If the ovaries are dissected out just 
previous to oviposition the young larvae can be seen within the egg 
membranes ; they are perfectly formed and show active movements, as if 
they were trying to find a way out of the egg. In the next degree, which 
is instanced by two species of Musca, namely, corvina, Fabr., var. 
vivipara Portschinski, and bezzii, Patton and Cragg, which are both 
blood-feeders, the larva is retained and nourished for a part of its 
life in the genital tract of the female, but is deposited while still young, 
and completes its growth under conditions similar to those of its allies. 
In the third degree the larva is retained until it is ready to pupate, 
and in consequence of its large size during the later stages the genital 
tract is greatly altered in its shape and relations. Glands are also deve- 
loped to provide nourishment for the growing larva. 

As the Tachinidae are not blood-feeders they need not be discussed 



THE PUPIPAROUS HABIT 



139 



here. Their pecuHar method of reproduction is the outcome of the cir- 
cumstances under which the larval stage is passed, for these flies deposit 
their eggs, or young larvae just hatched from the eggs, 

Origin of 

in the bodies of other larger larvae, usually those pupiparous habit 

of Lepidoptera, and a reduction of the immature 
stages is a necessary condition of their existence. The larval stage 
must be completed before the host pupates, or immediately after, lest 
the food supply should be exhausted. In the other two cases there is no 
such apparent necessity for an acceleration of the stages, and we must 
look elsewhere for an explanation of the origin of the habit. Probably 
two factors enter into it. In the first place, the larva while retained in 
the body of the active female will avoid a large proportion of the dangers 
to which a free larva is subjected, both from predaceous insects and 
from birds, and from accidental conditions such as loss of food 
supply, exposure to adverse conditions of temperature and moisture, etc. 
A larva which only leaves the body of the female when it is ready to pro- 
tect itself by pupation has obviously a better change of reaching the 
mature stage than one which has to live free for a considerable period. 
Secondly, the rich supply of food which blood-sucking insects can obtain 
appears to have some relation to the pupiparous habit. Although the 
number of Diptera which feed on blood is exceedingly small in propor- 
tion to the size of the order, the number of pupiparous forms is very high, 
including the whole group known as the Pupipara, the genus Glossina, 
and some Muscids. Even in Philaematomyia insignis a shortening of the 
first stage can be noticed, for the eggs are much larger when laid than 
one would expect for the size of the fly, and the larvae hatch from them 
at a much earlier period than the larvae of other Muscids under iden- 
tical conditions. The subject is a very obscure one, but the association 
of the blood-sucking habit with the pupiparous habit is clear enough, and 
one should always be on the look out for larviparous forms among those 
known to suck blood, whether they are biting flies or not. 

The term ' pupiparous ' is really a misnomer, for the instar which is 
produced from the mature female is a full-grown larva, which does not 
pupate until it is in suitable surroundings. The larva of Glossina when 
born is able to move about until it finds a suitable place for pupation. 
That of Hippobosca is not motile, but passes into the pupal stage at the 
place where it leaves the female. 

Musca hezzii is an example of the second degree, in which a young larva 
is produced. In the early part of its life the larva is nourished by the 
mother, while in its later stages it obtains food for itself after the 



140 



MEDICAL ENTOMOLOGY 



manner of its kind. Musca corvina (var. vivipara) appears to have 

^ .. a similar life history; in all probability the habit is 
Musca bezzii j ' r j 

by no means a rare one. 

In Musca bezzii there are only two ovarioles, each constituting the 
ovary of its own side. As in the other Muscids, the ovariole is divided 
into a number of follicles, in each of which there is an ovum, more or 
less mature. But as only one larva can be contained in the uterus at one 
time, the ova in the two tubes are never in the same state of develop- 
ment, the lowest one of one side being always more advanced than that 
of the other. The upper follicles, also, are not stretched out in line with 
the first, but are bent over and appear to be attached to the side of the 
large lowest follicle containing the mature or nearly mature egg. This is 
a result, partly at least, of the alteration in the position of the parts of the 
reproductive organs in consequence of the presence of the larva, which 
thrusts the ovaries forward and to the dorsal side as it grows. The two 
ovarioles distal to the last follicle are continued downwards as oviducts, 
which unite in the ordinary manner to form a common oviduct, which 
leads in turn to the genital opening. The walls of both the paired and 
unpaired oviducts are very well supplied with muscular fibres, which are 
arranged in definite transverse and longitudinal bands. The transverse 
bands are very well developed at the distal end, and form a sort of 
sphincter around the genital orifice. 

The appearance and relations of the common oviduct, which may 
be termed here the uterus, differ entirely according to the contents. 
When it is empty it forms a simple elongate and rather spindle- 
shaped chamber, resembling that of the oviparous species of Musca, 
but of greater length. But when it contains a larva ready for birth it 
is enormously increased in size, and is pressed forward into the anterior 
and ventral region of the abdomen ; its upper end, at which the mouth 
of the larva is situated, is expanded beyond the point at which the 
paired ducts unite, so that the latter appear to join the uterus some 
distance behind the anterior end. The whole chamber is bent a little in 
accordance with the attitude of the larva, which does not lie stretched 
out in a straight line, but is arched so that its lower border is concave. 

When the uterus is empty it is usual to find a nearly mature egg in 
one of the follicles, and, vice versa, when the uterus contains a growing 
larva the ripest egg is still immature. The two ovarioles function 
alternately, first one and then the other producing a ripe ovum and 
passing it into the uterus. 

The stay of the larva in the uterus is not a long one, and there is 



GLOSSINA: REPRODUCTIVE ORGANS 141 



no elaborate arrangement of milk glands, such as is found in the true 
Pupipara, for the nourishment of the growing young. There is a single 
pair of accessory glands, which open at the upper end of the common 
oviduct ; these are certainly much larger than those found in the 
oviparous forms. 

The spermathecae resemble those of Miisca, two of them, however, 
being inserted by a common duct. All three ducts are very much coiled. 

The following account of the female reproductive tract of Glossina is 
taken from Roubaud. The writers have not had the opportunity of 
examining Glossina in the fresh state. 

The apparatus consists of two parts, the ovaries and their accessory 

organs (spermathecae and milk glands), and the unpaired portion, the 

oviduct, uterus, vagina, and the common duct of the 

' to ' Glossina 

milk glands. 

The ovaries are of the same type as those of Miisca bezzii. There 

is one ovariole on each side, containing at most four or live follicles, 

and the two sides function alternately, first one and 
111 1 -11 Ovaries 

then the other producmg a mature egg m the lowest 

follicle. As in bezzii, the upper follicles are so much outgrown by 

the lowest one that they appear to be attached to its lateral aspect. 

Each ovarian tube opens by a short canal into the median unpaired 

oviduct, which in turn opens, after a slight dilatation, into the upper 

end of the uterus. The walls of the ovarian tube are composed of an 

external layer of muscle fibre, and an internal fibrous layer adherent to 

this. 

The uterus is a large distensible sac, the dimensions of which neces- 
sarily vary according to the state of the development of the larva ; when 

the larva has attained to full growth it occupies almost 
1 1 rill T -111 Uterus 

the entire ventral region oi the abdomen. It is held 

in position by a rich tracheal network, best developed on the ventral 

surface and at the sides, and by various muscles, the arrangement of 

which has been described by Minchin. The disposition of these is 

sufficiently indicated in the figure (Plate XXX) ; in addition to those 

shown there is a large unpaired muscle in the middle ventral line which 

connects the uterus with the ventral abdominal wall. These muscles 

support the heavy uterus during gestation and are able to adjust its 

position in the abdominal cavity. 

The walls of the uterus are composed of an external tunic of muscle 

fibres, arranged in longitudinal, circular and oblique bands, and a fine 

chitinous lamina on the internal aspect. The oviduct, which leaves the 



142 



MEDICAL ENTOMOLOGY 



organ on the dorsal side of the upper end, is of a similar structure. Im- 
mediately behind the entry of the oviduct into the uterus there is a 
conical elevation of the wall, on the top of which are situated the orifices 
of the ducts of the spermathecae and nourishing glands. At this point 
the chitinous and muscular layers of the wall are greatly increased in 
thickness. 

The posterior contracted portion of the uterus forms the vagina. It 
has a structure similar to that of the uterus, the chitinous lamina 
of the wall being, however, increased in thickness. It is provided with 
dilator muscles by means of which the cavity can be widened at the 
moment of the birth of the larva. 

The spermathecae are small rounded spheres of a yellow colour, the 
tint being due to the thick chitinous lamina which forms their internal 

Spermathecae wall. External to the chitinous layer, which in pal- 
palis and tachinoides is adorned with small raised areas 
on the internal surface, there is an investment of a single layer of highly- 
vacuolated cells. In G. fiisca the raised areas are absent, and the outer 
investment consists of two layers of non-vacuolated cells. 

The two spermathecae are united in a common cellular investment, 
and open, each by a fine canal, into the dorsal aspect of the uterus. 
The inner walls of these ducts show an arrangement of chitinous 
spirals like those of a tracheal tube, but with the rings more separated 
and less numerous. The external cellular covering is thin and the cells 
are without vacuoles. The two ducts open into the uterus at the same 
point, and here the circular muscle fibres are arranged to form a 
sphincter. 

After fertilization the cavity of the spermatheca and its duct is 
filled with spermatozoa, which are also found within the cavity of the 
uterus at the level at which the ducts open. This is also the point 
at which the mouth of the larva is situated during gestation, and one 
might suppose, Roubaud remarks, that the spermatozoa which are not 
used up in fertilization are absorbed by the larva, as has been stated 
by Berlese to occur in Melopliagits, along with the secretion of the 
nutrient glands. 

The nutrient glands, or milk glands, are characteristic of the genital 

apparatus of the pupiparous Diptera. In Glossina they are much 

branched tubular glands, which are situated dorsally 
Milk glands , • , r , j i_ 

on each side oi the uterus and open mto its cavity by a 

common duct just behind the opening of the ducts of the spermathecae. 

The dimensions and the amount of ramification of the glands depend 



PLATE XXX 



Figure 1. Genital apparatus of Glossina palpalis, ? , dorsal 
view, after Roubaud. 

O., the oldest egg. o'., nurse cells of the second foll- 
icle. Od., oviduct. Od. C, common oviduct. Sp., 
spermathecae. C. Sp., their duct. GL, uterine glands. 
C. gl., their common excretory duct. Ut., uterus. V. 
vagina. M.r., retractor muscles of the uterus. M.p.d., 
M.p.v., dorsal and ventral protractors of the uterus. 
M.d., Dilator muscles of the vagina. The figures 1. 
2, 3, ... 8 represent the relative age and order of suc- 
cession of the different ovules. 

Figure 1. The genital apparatus of Musca bezzii, ? . a.g., 
accessory gland. Other letters as before, x 10. 

Figure 3. The genital tract of Melophagus oviiiiis, ? , dissected 
from the body, and seen from the dorsal side. After 
Pratt. X 33. med. ovi., median oviduct. pa. ovi., 
paired oviduct. rec. sem., receptaculum seminis. 
a.m.gl., anterior milk glands, ov., ovary, p.m.gl., 
posterior milk glands. U., uterus, vag., vagma. 

Figure 4. Longitudinal section of the two ovaries, the paired 
oviducts, and the receptaculum seminis, of Melophagus 
ovinus-. ovar. 1., ovar. 2., the two ovarioles of each 
ovary. 1, 2, 3, . . . 8, the different follicles ui the order 
in which they discharge their ova. n.ce., nutritive 
(nurse) cells, ger., germarium. After Pratt. X 52. 
(reduced from original.) 



I 

i 

il 



GLOSSINA: REPRODUCTIVE ORGANS 143 



upon the age of the fly and stage of the reproductive process. In 
young females which have not yet begun gestation the diameter of 
the principal branches is twice that in the gravid females, but the 
ramifications are much less numerous, and each gland is limited to 
a small white tuft at each side of the uterus. 

In females in an advanced stage of gestation these glands are seen 
to have taken on an excessive increase. On the dorsal surface there are 
four principal branches which arise from a common longitudinal trunk 
and pass over all the length of the growing larva. The lateral 
branches, passing round the sides and towards the ventral surface, divide 
up into innumerable ramifications, which, anastomosing with one 
another, produce a rich network of glandular tubes throughout the 
abdomen ; the ultimate terminations end blindly. They penetrate into 
the interstices of the fat body, but there is no continuity between the 
two. The cellular walls are simply in intimate contact. 

The epithelium of which these glands are composed presents different 
appearances in the different regions. In the proximal part of the organ, 
a little in advance of the union of the two principal trunks to form 
a common canal, the secretory cells are cubical, highly vacuolated on 
their internal aspect, and enclose a lumen which is circular on section 
and relatively large. Internally there is a fine layer of chitin, from 
which a series of spine-like projections pass into the lumen. The nuclei 
are small and spherical, the chromatin network indistinct, and there is a 
large centrally placed acidophile nucleus. In sections through the young 
ramifications, on the other hand, the secreting cells are higher, and 
the lumen correspondingly reduced. The cells are only a little vacu- 
olized, the chromatin network is distinct, and the nucleus usually 
eccentric. There is no trace of the chitinous lamina internally. 

Sections through the common duct show that it is in reality com- 
posed of two ducts which are united in a common muscular investment. 
The epithelium is replaced by a layer of small hypodermal cells, and the 
internal chitinous lamina is much increased, and presents an arrangement 
similar to that of the ducts of the spermathecae. The glands open on a 
small conical papilla which may be regarded as a sort of teat, since it is 
directed towards the mouth of the larva. 

The cytoplasm of the cells of these glands has a remarkable affinity 
for stains, which makes the finer details of the histology difiicult to 
follow. It is easily stained in the fresh state by neutral red, methylene 
blue, etc. 

The fluid secreted by these glands is of a milk white colour when 



144 



MEDICAL ENTOMOLOGY 



seen in bulk, and contains a large number of granules in suspension. 
Some of these are fatty, but the majority appear to be of an albuminous 
nature. The fluid is used, exactly as in mammals, for the nourishment 
of the young. It is not, however, entirely absorbed by the larva, 
but is retained in considerable quantity in the stomach, to serve for 
the nourishment of the larva after it has left the body of the 
parent. 

The normal physiology of reproduction may be summarized as follows. 
The lowest follicles of the ovary produce eggs in turn, and as each is 
fertilized it passes down into the uterus. It has been 

Reproduction 

shown by Roubaud that, if fertilization does not occur, 
the egg is retained in its position in the ovarian sheath, while the eggs 
which should be produced after it continue their growth up to a certain 
point. Fertilization, in fact, determines the passage of the egg to the 
uterus, but not the maturation of the eggs contained in the ovarian tubes. 
When it has passed into the uterus after fertilization the egg hatches, and 
a young larva emerges. The larva is free in the cavity of the uterus, but 
the walls of the latter, by virtue of their muscular tissue, contract around 
it, accommodating the size of the cavity to the size of the larva as it grows. 
The mouth of the larva is situated at the ' teat ' formed by the entry of 
the ducts of the milk glands into the uterus, and the larva, by a special 
apparatus, sucks the fluid from the glands into its stomach, which is 
always full under normal conditions. The posterior end of the larva is 
placed at the vulva, the muscles surrounding which are so arranged as to 
enable the cavity to be placed in communication with the external air, in 
order to allow the larva to breathe through the stigmata at its poste- 
rior end. The stay of the larva in the uterus is about ten to eleven days. 
When mature it is expelled by the contraction of the muscular coat of 
the uterus ; its stomach at the time of birth is still full of the milk derived 
from the mother. It then crawls away to pupate. 

The reproductive process in Glossina has been shown by Roubaud to 
be easily influenced by changes in the environment. As these have a 
direct bearing on the bionomics of the fly they will be discussed in that 
connection. 

Whereas the pupiparous habit in Glossina is markedly at variance with 

the method of reproduction in the rest of the Muscidae, in the 

Pupipara the habit is the rule, and forms the distin- 
The Pupipara . . . 

guishing character of the family. The subject is of 

great interest, and even before the practical importance of it was 
recognized it had already attracted a good deal of attention from 



REPRODUCTIVE ORGANS: MELOPHAGUS 145 



entomologists. A very full account of the reproductive organs of Meloph- 
agus has been written by Pratt. The conditions in Hippobosca are very 
similar, and both resemble Glossina in the essential features, the 
similarity forming a good example of convergent development. The 
fact that Glossina is pupiparous does not, of course, indicate any direct 
connection by descent between that genus and the Pupipara ; the latter 
form a class by themselves, and are only distantly related to the 
Muscidae. 

In Melophagtis (Plate XXX), the ovaries are arranged on the same 

plan as those of Glossina, but there are two ovarioles in each ovary 

instead of one. The same alternation in the produc- . . 

... , . WIelophagus 

tion of the eggs is observed, but it is in this case a 

little more complicated, for not only do the ovaries alternate, but also the 
ovarioles in each ovary, so that only every fourth larva is produced from 
any given ovarian tube. The peritoneal coat of the ovary is much 
thicker than in most Diptera, and presents some remarkable peculiarities 
which have been described in detail by Pratt. 

The oviducts present a striking feature, not found in any other 
Diptera, namely, the transformation of a part to form the recep- 
taculum seminis. Each oviduct is short, and joins its fellow of the 
opposite side to form a slight dilatation in the middle line near the 
point at which the milk glands enter the cavity of the uterus, and it is 
here that the sperms are found in the fertilized female. In the virgin 
female the oviducts are not in line with the uterus as is usually the 
case, but join it at a right angle, that is to say, they are more or less 
perpendicular to the long axis of the body. When gestation is advanced 
the angle becomes very acute as the anterior end of the uterus passes 
forward with the growth in length of the larva. 

The uterus is broad, and occupies a considerable proportion of the 
space within the abdomen, crowding the other viscera forwards when it 
becomes enlarged. It is compressed dorso-ventrally, and is held in 
position by large tracheae and muscles which run between it and the 
abdominal wall, as in Glossina. The wall is composed of a thick inter- 
lacing network of muscle fibres, internal to which there is the usual 
chitinous intima. In the lower part of the cavity the intima is thick, 
and is in continuity with, and of the same appearance as, the integument, 
of which the lower part of the uterus and the vagina are evident 
invaginations. In the upper part of the cavity the chitinous intima 
is very thin, and is thrown into numerous folds when the lumen is 
empty. The young larva is retained in this anterior portion for the 
19 



146 



MEDICAL ENTOMOLOGY 



first part of its period of growth, until its posterior end, which bears 
the stigmal plates, comes to lie in the vulva, through which its supply 
of air is drawn in. 

There are two pairs of milk glands, both in Hippohosca and in 
Melophagiis ; one pair in the latter is rudimentary, and does not 
assist in providing nourishment for the larva. The functional glands 
resemble those of Glossina so closely both in their structure and 
disposition as to call for no further remark. 

The Spermatozoa of Diptera are long filiform bodies (Plate XXIX, fig, 

6), which frequently exhibit active lashing movements. At one end there 

, „ is a slight swelling containing the nucleus, which is 

TnG Sp6rni3tozo3 

difficult to stain properly. They do not present many 
dififerences in the different families, and their only importance from the 
present point of view lies in the possibility that they may be mistaken for 
parasitic organisms, such as spirochaetes or filaria. They are frequently 
seen free in dissections of male insects, having escaped through the 
rupture of the testes or the seminal vesicle, or in the female through 
rupture of the spermathecae. When once recognized, however, they 
are not likely to be mistaken for anything else. 

The spermatozoa arise from the germinal cells of the testes by a 
process corresponding to that which produces ova in the female. Here- 
ditary transmission of parasites through the male has not yet been 
suggested in insects. 

THE NERVOUS SYSTEM 

. A brief note on the nervous system will suffice here, as all that is 
necessary for the parasitologist is to be able to recognize the parts when 
met with in sections and dissections. 

The nervous system of an insect consists of ganglia and nerves ; the 
latter, as in the vertebrates, are either motor or sensory. The arrange- 
ment of the parts in the various groups is best under- 
Development \. . . . ? \. . , 

stood by a reference to their origm. In a very simple 

insect there would be, theoretically, one ganglion, giving off motor nerves 
and receiving sensory nerves, on each side of each segment, and such 
a condition is in fact approached in some known forms. In later forms the 
ganglia have become fused with one another to a greater or less extent ; 
the fusion results, as it has done in the vertebrates, in the gradual 
accumulation of the ganglia in the anterior part of the body, and par- 
ticularly in the head. Each segment of the head may be supposed 
to have had originally its own pair of ganglia for the control of its own 



THE NERVOUS SYSTEM 



147 



appendages. These, however, have become fused into a single more 
or less compact mass termed the brain. Similarly in the thorax, the 
three ganglia are usually, and always in the Diptera, fused to one mass. 
The abdominal ganglia may either remain distinct, or they may fuse 
with one another and even with the thoracic ganglion. In all cases 
the two bilateral ganglia of each segment are found to be fused with 
one another, the double ganglion lying in the middle line. 

The brain, then, consists of six fused ganglia which belong to the head 
segments and supply the head appendages. As one might expect, 
the distinction between the several parts is not evident in the highly 
specialized Diptera, as far as the external appearance is concerned, and 
we find a rounded mass, generally considerably longer in the transverse 
diameter than in the antero-posterior, from which are given off nerves 
to the antennae, the palps, and other appendages. The lateral portions 
send out many radiating fibres for the supply of the compound eyes, 
and are distinguished as the optic lobes, while the middle portion, 
which may appear to consist of a single mass or two bilateral halves, 
is known as the central body. But of the six segments in the head 
three, or two where the third segment is wanting, as it is in the 
Diptera, are preoral, while the last three are postoral. The mouth 
lies, therefore, between the anterior and posterior parts of the brain, 
while the alimentary tract lies dorsal to the nerve cord and ganglia in the 
rest of the body. The tract has thus to pass through the brain to gain 
its subsequent position, and its anterior part is consequently encircled 
by a ring of nervous tissue. The particular part of the tract which pierces 
the brain differs in the different genera. In Tabaniis, as already pointed 
out, the pharynx is anterior to the brain, which is pierced by the 
oesophagus, as is also the case in the Muscidae, whereas in the 
mosquitoes the pharynx is mainly behind the brain ; the portion of the 
tract which pierces its substance is the chitinous tube connecting the 
buccal cavity with the pharynx. 

The brain is thus divided into two parts, one which lies above the 
alimentary tract (strictly speaking, anterior to it), and is known as the 
sHpra-oesophageal ganglion, and one which lies below it, and is known as 
the stib-oesophageal ganglion. From the latter are given off two stout 
nerve trunks which soon unite with one another and pass backwards to 
the thorax, where they join the compound thoracic ganglion. From this 
emerge the nerves which supply the muscles of the thorax, and at its end 
a nerve trunk which passes to the first abdominal ganglion. Each of the 
abdominal ganglia gives off a pair of nerves for the supply of the muscles 



148 



MEDICAL ENTOMOLOGY 



and organs of the abdomen, and sends a nerve cord to the ganglion 
immediately posterior to it. 

The actual conditions to be met with in the Diptera are well 
exemplilied by a comparison of Anopheles, Tabanus (Plate XXVII, 
fig. 1) and Musca (fig. 4, ibid.). In each of these the brain forms a 
compact mass which is pierced by the alimentary tract and gives off a 
large trunk on each side posteriorly. These nerve cords lie at first external 
to the oesophagus as it emerges from the brain, but as they converge 
to join one another they come to lie below it. In each of these forms 
the thoracic ganglia are fused with one another to form a large mass which 
lies in the middle ventral line in the anterior part of the thorax, but well 
marked differences are seen as regards the abdominal ganglia. \n Ano- 
pheles these are six in number, and are well separated from one 
another. In Tabanus five abdominal ganglia can be distinguished, 
but they are set close together, looking like a string of small white beads. 
In Musca the abdominal ganglia are fused with the thoracic to 
form a large compound ganglion, from which many fine nerves pass 
backwards to the abdomen. There is thus a well-marked relation 
between the concentration of the nervous system and specialization in 
other directions. 

The ganglion cells are of considerable size, and show up well 
in sections stained with haematoxylin, so that the separate parts 
of a compound ganglion can be readily recognized. In the brain 
there are certain curious and highly complex structures, known as 
the ' mushroom bodies ', which stain brightly with eosin, and are con- 
spicuous in sections of the head. These are connected with many 
commissures and tracts within the substance of the brain ; for an 
account of them the reader is referred to Berlese's work. 



Literature 

Annett, H. E., Dutton, J. E. Report of the Liverpool Expedition to Nigeria, part 
and Elliot, J. H, ii. Thompson Yates Laboratories Reports, Yol. iv, 

' Part i, 1901. 

■ -- Contains an account of the proboscis and sucking 

apparatus of Anopheles costalis, with numerous 
coloured drawings. 

Berlese, a. Gli Insetti. Vol. i. Embriologiae Morphologia. Societa 

Editrica Libraria, Milan, 1909. 
A book of 1004 pages, Crown quarto size. It deals 
with all orders ot insects, is very well illustrated, 
and contains a large bibliography, with references 
■ " to all the older papers. 



LITERATURE ON STRUCTURE OF DIPTERA 149 



Christophers, S. R. 



COMSTOCK, J. H. 
and Needham, J. G. 

Cragg, F. W. 
idem 



Graham-Smith, G. S. 



Grassi, B. 



Kraepelin, K. 



LowNE, B, T. 



MlALL, 1.. C. 

and Denny, A. 
Newstead, R. 



Newstead, R. 



Nuttall, G. H. F. 
and Shipley, A. E. 



The Anatomy and Histology of the Adult Female 
Mosquito. Reports to the Malaria Committee of 
the Royal Society, fourth series, 1901. 

Twenty pages, six plates. A good working account of 
the structure of the female Anopheles. The figures 
are very instructive. It contains no references to 
literature. 

The Wings of Insects. American Naturalist, Vol. 
xxxii-xxxiii, 1898-9. 

A comparative study of wing venation. 

The Structure of Haematopota pltivialis. 

Studies on the Mouth Parts and Sucking Apparatus 
of the Blood-Sucking Diptera, No. 1. Philaema- 
fomyia insignis. No. 2. Some Observations on the 
Parts in the Nematocera. No. 3. Lyperosia minuta. 
No. 4. The Comparative Anatomy of the Proboscis 
in the Muscidae. Scientific Memoirs by the Officers 
of the Medical and Sanitary Department of the 
Government of India, Nos. 55, 54, 58, 59 and 60. 

Some Observations on the Anatomy and Function of 
the Oral Sucker of the Blow-Fly (Callipohora ery- 
throcephala) . Journal of Hygiene, Yol. xi, No. 3, 
1911. 

A full and very well illustrated account of the labella, 
with special reference to the structure and mode of 
action of the pseudotracheal membrane. A most 
valuable paper. 

Ricerche sui Flebotomi. Memorie delta Societa 
Italiana delle Scienze, ser. 3., torn. xiv. Rome, 
1907. 

A complete account of the structure of Phlebotomus. 

Not easy to procure. 
Zur Anatomie und Physiologie des Russels Von Musca. 

Zeit. f. Wissenschaftliche Zoologie, Bd. 39, 

1883. 

A complete account of the proboscis of Musca domes- 
tica, very well illustrated. It should be read in con- 
junction with Graham-Smith's paper. 

The Anatomy, Physiology, and Development of the 
Blow-Fly. London, 1890 — 1895, two volumes. 

A standard work. Rather difficult to procure. 

The Structure and Life History of the Cockroach. 
London, 1886. (Lovell Reeve & Co.) See page 9. 

The Papataci Flies (Phlebotomus) of the Maltese 
Islands. Bulletin of Entomological Research, 
Vol. ii. Part i, 1911. 

Contains an account of the internal anatomy. 

A Revision of the Tsetse-Flies [Glossina), based on a 
study of the male genital armature. Bulletin of 
Entomological Research, Vol. ii, Part 1, 1912. 

The Structure and Biology of Anopheles. Journal of 
//jigjewe. Vols, i-iii, 1901— 1903. 



150 



MEDICAL ENTOMOLOGY 



OSTEN SACKEN 



Packard, A. S. 



Pratt, H. S. 



ROUBAUD, E. 



A complete account of Anopheles maculipennis, con- 
taining an extensive bibliography. Very valuable to 
those engaged in the study of malaria. The illustra- 
tions are extremely good. Little has been added to 
our knowledge of the anatomy and physiology of the 
mosquito since this was written ; the views of previous 
workers are discussed fully in the text. 
An Essay of Comparative Chaetotaxy. 
Trans. Ent. Soc. Lond. 1834. Part iv. 
This paper marked the beginning of the study of chaeto- 
taxy in the Diptera, and is the main source of the 
nomenclature at present in use. 
Textbook of Entomology. Macmillan, London and 

New York, 1898. 
Very useful as an introduction to the structure of 
insects in general, and for reference. Unless one 
has had special training in Entomology, either this 
book or that of Berlese is almost a necessity. It 
contains references to the older literature. 
The Anatomy of the Female Genital Tract of the 
Pupipara as observed in Melophagus ovinus. Zeit, 
f. Wiss, Zool., B. 66, 1899. 
La Glossina palpalis. Sa biologie, son role dansl'eti- 
ologie des Trypanosomiases. These de Doctorat cs 
Sciences Naturelles, Paris, 1909. (Extract from the 
Rapport de la Mission d' etudes de la maladie du 
sommeil au Congo Francais, 1906-1908.') 
Contains perhaps the most complete account of the 
anatomy of Glossina, dealt with from a comparative 
point of view. 
Generations und Wirtswechel bei Trypanosoma und 

Spirochaete. Arb. Kais. Gesund. B. 20, 1904. 
The well-known paper on the trypanosome of the 
Little Owl, etc. It contains an account of the 
anatomy of Culex. 
The Anatomy of the Proboscis of Biting Flies. I. 
Glossina, Memoir XVIII, Liverpool. School of 
Tropical Medicine, 1906. II. Stoinoxys, Ann. of 
Trop. Med. and Parasitl, Vol. i.. No. 2., 1907. 
The Alimentary tract of the Mosquito. Proceedings 
of the Boston Society of Natural History, Vol. 
xxxii, No. 6. 1905. 
Deals with the morphology and development of the parts. 
The Taxonomy of the Muscoidean Flies, including 
Descriptions of New Species. Smithsonian Mis- 
cellaneous Collections, Vol. ii. Washington, 1908. 
Contains an account of the external anatomy and its 
nomenclature in relation to systematic classification. 

See also Gordon Hewitt, Minchin Patton and Cragg, Tulloch at end of Chapter IV. 



SCHAUDINN, F. 



Stephens, J. W. W. 
and Newstead, R. 



Thompson, M. T. 



TOWNSEND, C. H. T. 



Note. — For an account of embryology and development, which ha\'e not been dealt 
with in this chapter, see Berlese, 



CHAPTER III 



SECTION 1 

THE ORDER DIPTERA : ORTHORRAPHA— NEMATOCERA 

The Diptera form a well defined and highly specialized group of insects, 
easily distinguished, in the great majority of cases, by the presence 
of only one pair of wings ; the second pair of other insects being 
represented by the halteres. The order is a large one, not less than 
36,000 forms being known at the present time, while new genera and 
species are constantly being added. The study of the group has re- 
ceived a special impetus since the economic importance of manj' of the 
species has become recognized. 

Before passing on to the classification and the detailed description 
of the important forms, it is necessary to refer briefly to the life 
history and early stages, and to explain certain con- 
nected terms in common use. Metamorphosis in the ""etamorphosis and 

^ . Early Stages 

Diptera is always complete, the ann-nal passmg through 

the separate stages of egg, larva, pupa, and imago. The eggs vary 
greatly in size and appearance, and will be described under the species 
to which they belong. They are always minute, often invisible to 
the naked eye or nearly so, and are laid in or near the food of the 
larva, in numbers which correspond as a rule with the number of ova- 
rioles in the ovaries. The larvae vary with their habitat and accord- 
ing to the family to which the imagines belong, the former factor 
exercising the predominant influence over their structure. Generally 
they are footless maggots, with an elongated and segmented body, 
consisting of a larger number of segments than can be distinguished 
in the adult. They may be aquatic or semi-aquatic in their habits, 
or they may live in decaying animal or vegetable matter, or in the 
excreta of animals. Although it is not necessarily the case that the larvae 
of allied forms resemble one another, as a general rule they do so, 
and a correspondence between the systematic position of the imagines 
and the structure of the larvae can be noted. 



152 



MEDICAL ENTOMOLOGY 



The more simple Diptera, such as are found in the Orthorrapha, 
have as a rule aquatic or semi -aquatic larvae, which move actively about 
by means of wriggling motions, or with the aid of posteriorly situated 
fins. The body is segmented, and the head, thorax, and abdomen may 
be well demarcated from one another. The larva feeds mainly on solid 
particles, such as animal or vegetable refuse, or on small animalculae, 
and is provided with mouth parts suitable for this purpose, the 
mandibles being often well developed. The alimentary tract is as a 
rule simple, and only slightly exceeds the length of the body, the coils 
being limited to the hind-gut. Larvae possessing a well defined head, 
with a pair of mandibles, are termed eiicephalous. In the higher 
Diptera the larvae usually live in a rich food material, such as animal 
refuse, dung, etc., and neither need not possess biting mouth parts, 
the mouth being adapted for the ingestion of the rich liquid fluid in 
which their lives are passed. The same condition has led to a cor- 
responding degradation of the rest of their structure. The head, for 
instance, since it has no longer to contain the mouth appendages and 
their muscles, is reduced until it cannot be recognized as such, when 
the larva is said to be acephalous; an intermediate form, in which 
the head, while yet recognizable, is inconspicuous, is termed hemi- 
cephalous. The larvae of the majority of Diptera are included under 
this latter group. Since larvae living in such material do not need 
to move about actively in search of food, they are generally unprovided 
with foot appendages, having at most small pseudopodia on the ventral 
parts of the segments, or thickened annular ridges at the junction of 
the segments, sufficient to enable them to gain a purchase on the 
substance in which they lie, while progression is brought about by 
rhythmical contractions and extensions of the body. On the other 
hand, as the outward form has become debased the internal structure 
has become specialized for the more rapid absorption and digestion 
of the food. The alimentary canal in these higher forms is al- 
ways greatly increased in length, as it is in the adult, and is coiled 
up in the abdomen ; the majority of the coils are situated in the 
posterior part, which is in consequence generally stouter than the 
anterior. 

The respirator}' system of the larva, owing to its constancj^ in certain 
groups, has been singled out as a point of importance in classification. 
Several forms are met with, dependent on the number and position 
of the stigmata. These are seldom placed segmentally, but are usually 
limited to the hind end of the body. From each stigma in this situation 



LARVAE OF DIPTERA 



153 



two lateral tracheae pass forwards through the body, giving oif 
branches to the tissues as thej^ go, and they communicate with the 
anterior respiratory openings when such are present. When there are 
stigmata on the first and last segments of the body (not counting the 
head) the larva is said to be amphipneustic, while if they are limited 
to the posterior end the term metapnetistic is employed. When 
stigmata are found along the sides of the body, an uncommon con- 
dition, the larva is said to be peripneustic. A larva may begin life 
in the metapneustic stage, and become amphipneustic later. The 
posterior stigmata are often conspicuous structures, and are usually 
recognizable with a hand lens. Since they differ in detail in closely 
allied flies, and often present the only recognizable distinctions between 
the larvae, they are of use in distinguishing species from one another, 
both in practical work when breeding for experimental purposes and 
for systematic classification. 

In many of the aquatic larvae of the Nematocera the structure of 
the respiratory system is specially adapted to their mode of life. In 
the larger species of Chironomiis the tracheal system is rudimentary 
and entirely closed, so that gaseous air is not taken into the body, 
the dissolved oxygen in the water, in all probability, being absorbed 
by the tracheal gills at the posterior ends of their bodies. These 
larvae, which live in tunnels at the bottom of pools, and even at 
great depths in lakes, have in addition a blood-red pigment — thus the 
name blood worm — which is believed to act as an oxygen carrier. 

Another nematocerous larva which lives permanently below the 
surface of water, in this case well aerated water, is that of Simiilium. 
It also has a closed respiratory system. The pupa of this type of 
aquatic larva has a large number of respiratory filaments, which are 
well adapted for the absorption of oxygen from water. 

The larvae of the smaller Chironomidae, and of some of the Culicidae 
(Corethra), which live among weeds at, or near the surface of water, 
also have closed respiratory systems, but in this case the blood is 
colourless. Their pupae have respiratory trumpets, and are air breath- 
ers. The aquatic larvae of Ceratopogon and Culicoides are good 
examples of this type. 

The larvae of Diptera usually cast their skins three times during 
the period of their growth, and although the moult is accomplished 
as a rule with little or no change except an increase in size, certain 
minor differences are to be noted in the several stages. This is of 
practical importance and must be taken into account in order to avoid 
20 



MEDICAL ENTOMOLOGY 



mistaking the several moults of one species for different larvae. In 
mosquito larvae the difference lies mainly in the length and ramifi- 
cations of the hairs of the exo-skeleton, the hairs tending to become 
more complex at a late stage in the life of the larva. In the Muscidae 
the form of the spiracles changes in a characteristic manner, the 
openings into the tracheae becoming much more convoluted. 

The' pupae of Diptera are of two main kinds. In one the larva 
casts its skin at the moment of pupation ; in the other it pupates 
within the larval skin, which is then termed the pupariitm. In either 
case the pupae absorb no food, but remain passive while their tissues are 
reorganized to fit them for the final and reproductive stage of their life 
history. The larval skin is cast in the Orthorraphic flies. In them 
the pupa is often active, especially in the aquatic forms, but more usually 
it is motionless, and may be fixed to some object in its environment. 
Such a pupa is termed ohtecta. In the higher Diptera the larval skin 
remains as an outer covering, within which pupation takes place, and 
the pupa is said to be coarctate. The distinction between the words 
pupa and puparium should be noted. The puparium has generally an 
elpngate ovoid shape, with a rounded contour in cross section ; the 
segmental markings can be faintly traced. The anterior and posterior 
stigmata can still be seen, and show the same markings as in the last 
larval stage. 

• The method of emergence of the imago from its pupa marks an im- 
portant distinction between the two main groups of the Diptera. In 
the simpler forms it emerges through a T-shaped slit on the anterior 
part of the dorsum of the thorax, while in the higher forms the anterior 
end of the puparium is removed as a small circular cap, a method which 
has given to the group the name Cyclorrapha. 

In some Diptera the life history is profoundly altered by the reten- 
tion of the early stages within the body of the parent, where thej' 
undergo a part or the whole of their period of growth. When the larva 
is thus retained and nourished until it is mature, the fly is said 
to be piipiparoiis, a term which, though sanctioned by long usage, is 
a misnomer, for the larva must necessaril}' leave the bod}' of the parent 
to pupate. The habit of producing larvae instead of eggs is found 
scattered somewhat indiscriminately throughout the Diptera, and occurs 
in varying degrees, as has alreadj' been pointed out in Chapter II. It 
is highly developed in the debased parasitic forms included in the 
Suborder Pupipara. 

: Because, of the enormousTsize of the order and the additions which 



CLASSIFICATION OF THE DIPTERA 155 



are constantly being made to it, classification and identification are 

somewhat difficult and unsatisfactory. The field worker 

1 11, 1, , , , Classification 

or parasitologist would do well, unless he has 

exceptional opportunities, to leave such matters in the hands of the 
specialist, and to content himself with a knowledge of those groups 
which are of practical importance. It is sufficient for most purposes 
to be able to ascertain with certainty, from a study of the external 
characters, which provide almost all the diagnostic features, that one 
is dealing with one species of fly and not two or more, and to be able to 
place the species in its proper genus. To do more than this requires 
in many cases an access to a voluminous and scattered literature, and 
also to the type specimens from which the species was originally de- 
scribed, or at least to a specimen named by a competent authority. The 
difficulty of identification has been greatly diminished by the keys which 
have been drawn up by specialists for such genera as contain species 
of practical importance. These will be found in this and the succeed- 
ing chapter, and it is hoped that with their assistance, and with some 
knowledge of external anatomy, the worker will be able to identify most 
of the important forms. A few named specimens are of great value 
for purposes of comparison. They may often be obtained in exchange 
for other material, or the worker may make a representative collec- 
.tion from his own district, and have the specimens identified. 

The following arrangement of the groups is mainly taken from 
Williston, who has adopted the classification of Brauer. 

The Diptera fall into three suborders, with secondary divisions, as 
.follows : — 

Orthorrapha. Larva with a jaw-capsule, or with a differentiated 

head. Pupa free or enclosed in the larval skin ; 
in either case escaping through a T-shaped 
slit on the dorsal side of the anterior end, 
or rarely through a transverse rent between 
the eighth and ninth abdominal rings. The 
imago has no frontal lunule or ptilinum. 
Nematocera. Antennae usually composed of more than six dis- 
tinct segments, the two basal ones frequently 
differentiated from the rest ; the flagellum 
always consisting of six to twenty or more 
segments, similar to one another. Palpi four 
or five jointed, and nearly always filiform. 
Wing venation simple or complicated. Larvae 



156 



MEDICAL ENTOMOLOGY 



- with either biting jaws or rudimentary mouth 

parts ; in the latter case they have thirteen 
segments and are perineustic. 

Brachycera. Antennae very variable in structure, the two basal 
segments, as a rule, differentiated from the 
third, which varies much in shape and struc- 

ture ; it may be annulated or not ; the arista 

is rarely dorsal, usually terminal. The vena- 
tion is complex, more so than that in the 
Nematocera. Larva with a rudimentary mouth, 
and either metapneustic or perineustic. 
Cyclorrapha. Larva without a differentiated head. Pupa al- 
ways enclosed in the larval skin — the puparium 
— the imago escaping through a circular orifice 
at the anterior end. Frontal lunule present, 
usually with a ptilinum. 

Aschiza. Antenna as a rule not composed of more than 

three segments, the third with a non-terminal 
arista. This group contains the three families 
Pipunculidae, Syrphidae and Platypezidae, in 
which the frontal suture is wanting. 

Schizophora. The antenna consists of three joints with an 
arista ; frontal suture always present. The 
larva has no distinct head, and is always 

- - amphipneustic. This group is often divided 

into the Calypterae, in which the squamae 
are well developed, and the thorax has a well 
marked transverse suture ; and the Acalypt- 

- - erae, in which the squamae are always small, 

and the thorax is without a complete trans- 

- verse suture. These subdivisions correspond 

- in the main to the Schizometopa and Holo- 

metopa of Brauer. The former is divided by 
some into the Anthomyiodia and the Muscoidea. 

PUPIPARA. Parasitic forms, often wingless or dropping their 

wings. Larvae born when ready to pupate. 
Very aberrant Diptera. 
In this and the following chapter the families which contain im- 
portant species will be particularly dealt with. For a more general 
account of the Diptera the reader should consult the Cambridge 



FAMILY CHIRONOMIDAE 



157 



Natural History (Insects, Part II), and for details of the genera Wil- 
liston's North American Diptera. 

THE NEMATOCERA 
FAMILY CHIRONOMIDAE 

Small midges from .5 to 14 mm. in length ; proboscis somewhat 
long ; antennae with four to fifteen segments, pilose in the female and 
plumose in the male. Eyes kidney-shaped ; ocelli absent in all species. 
Thorax strongly arched, scutellum and metanotum small. Wings as a 
rule straighter in the male than in the female ; costal vein terminating 
at the extremity of the third longitudinal vein ; subcostal or auxiliary 
vein not well defined ; first longitudinal vein distinct and abutting 
the anterior border of the wing ; second longitudinal vein inconspicuous, 
and sometimes absent ; third long vein well developed, often arising 
from the first and ending at the anterior border of the wing, rarely 
at the point. The fourth vein arises from the base of the iving, 
and is well developed up to the point at which it is united to the 
third vein ; it may be forked. The fifth vein is nearly always 
forked; the sixth and seventh veins are incomplete or often wanting. 
The wing is rough or hairy, but never clothed with scales. The 
halteres are bare. The legs are never elongated, and the tibiae usually 
terminate in a short spur. The abdomen is long and slender. 

The Chironomidae are common midges, many of which are nocturnal 
in their habits. During the rainy season in the tropics, they are 
seen in large numbers round a light, the majority of these prove 
to be males. Their larvae are the well-known blood-worms found in 
streams and stagnant pools. Some of them build for themselves 
characteristic tunnels of mud at the bottom of the pool, while others 
move about freely in the water or wet soil. A few pass their early 
stages under the barks of trees. The family is an enormous one, 
and is widely distributed. Kieffer recognizes five subfamilies, of 
which only one, the Ceratopogoninae, is known to contain blood- 
sucking forms. 

The eggs of the Chironomidae are small and ovoid, or long and 
pointed at their extremities, and are laid either in a gelatinous string 
of mucus or separately. The larva usually consists of thirteen seg- 
ments, and is encephalic and amphipneustic ; its head is directed 
downwards, and the mandibles are well developed. On the ventral 
surface of the first thoracic segment, and on the extremity of the last, 



158 



MEDICAL ENTOMOLOGY 



there are one or two pseudopods armed with bristles or hooks. 
On the ventral surface of the eleventh segment, and the extremity 
of the twelvth, there are delicate hnger-shaped processes, usually four 
in number ; these are the tracheal gills. The pupa is free, and either 
lives floating in water without any movements, or rests on the 
bottom of the pool. It has a tuft of delicate white threads on the 
dorsum of the thorax, which serve as breathing tubes ; or it may 
have a pair of respiratory trumpets. 

SUBFAMILY CERATOPOGONINAE 

Small to very small flics, from I to 2 mm. in length, seldom 
larger ; antennae of fourteen segments, the first usually large and 
somewhat flattened, the last five in the male larger than the others; 
the whorls of hairs are relatively short in the female and long in the 
male. Palpi either of four or five joints, seldom of three. Thorax 
strongly convex, and not produced above the head. Wings flat and 
covering each other when in repose. Costal vein ending at the 
extremity of the third longitudinal vein; second longitudinal vein 
absent, and the first and third always larger and better marked than 
the others; third and fourth generally united by a transverse vein; 
the fourth, which is usually bifurcated, is not united to the fifth. 
Legs well developed and of medium length ; femur often armed with 
spines on the lower surface. Larva without pseudopods or long hairs, 
or in some cases with thoracic pseudopods and with hairs. 

The following genera contain blood-sucking species : — 

Genus Tersesthes, Townsend 

Palpi three-jointed and longer than the proboscis ; first segment the 
shortest, second segment swollen, the third straight and furnished 
xvith a tuft of hairs at its extremity ; proboscis nearly as long as the head. 
Eyes kidney-shaped, and broadly separated at the vertex; ocelli absent. 
The antennae of the female are inserted into large circular depressions 
in the middle of the front, and consist of thirteen segments. 
The first segment is the largest, and is shaped like a flattened sphere ; 
the second is more elongate but less broad, the third to the twelfth are 
subglobular and equal in length, and the thirteenth segment is an elon- 
gated cone. Thorax not produced above the head, but a little broader 
than it, and without a transverse suture. Scufellum prominent. Wing 
studded with minute hairs ; first and second longitudinal veins better 



GENUS CERATOPOGON 



159 



developed than the others, and abutting the basal third of the wing 
border ; third longitudinal vein reaching nearly to the point of the wing ; 
fourth and fifth veins bifurcated : sixth and seventh not well developed. 
Legs slender, coxae not elongated, spurs on the hind tibiae prominent, 
those on the others weak ; metatarsus elongated ; pulvilli absent. Ab- 
domen elongated, consisting of seven segments ; ovipositor formed of two 
club-shaped processes. 

This genus at present contains the single species T. torrens. Town- 
send, which is found in North America, at a height of 7,000 feet ; it 
bites horses and other animals, usually on the head, ears and eyes. 
Its life history is not known. 

Genus Mycterotypus, Noe 

Noe created this genus for the two species A^3^ bezzii, and My. irritans 
from the South of Europe, which are said to be voracious blood-suckers,- 
biting human beings as well as animals, and causing inflammatory 
swellings. A. Weiss has recently described another species My. laurae 
from North Africa. According to Kieffer it is not quite certain whether 
the genus Mycterotypus is a good one; further observations on the 
species may show that they belong to one of the other genera of the 
Ceratopogoninae. 

Genus Ceratopogon, Meigen 

Head somewhat flattened in front, and prolonged into a moderately 
long proboscis. Antennae of fourteen segments in both sexes ; first 
segment large and shaped like a fiattened sphere, the succeeding 
eight or ten oval in shape, and in the male furnished with long plu- 
mose hairs ; in the female the hairs, which may be long or short, are 
verticillate. The last segments are more elongate and have short hairs. 
Thorax strongly arched, but never produced above the head. Wings 
held in a horizontal position in repose, and usually rough owing to the 
presence of small hairs closely applied to the surface ; third longitudinal 
vein either joined to the subcostal by a transverse vein, or united to it in 
part or the whole of its length. The fourth longitudinal vein is forked 
and joined to the third by a transverse vein. The fifth is also bifur- 
cated, and there is often a forked vein, free at its basal end, between 
the third and fourth veins. The sixth and seventh veins are rudiment- 
ary. The legs are strong and of moderate length ; the femora are 
neither spined nor swollen ; the hind metatarsus is longer than or 
equal in length to the succeeding joint ; the claws are simple and 



160 



MEDICAL ENTOMOLOGY 



equal ; the empodium is well developed, and almost as long as the claws. 
The abdomen consists of eight segments ; the male claspers have basal 
processes without any appendages ; the terminal portion is long and 
gradually drawn out into a point. 

All the species of this genus are small, the limit of length being 
from 1 to 3 mm., and they are consequently not very easy to see when 
they bury themselves among the hairs of the host ; they are easily 
recognized, however, when they become replete with blood. They 
often occur in large numbers, and are most frequently met with near 
water or thick undergrowth, seldom entering houses. They attack 
men and animals, and often cause great distress on account of their 
numbers and of the irritation produced by their bites. Some of the 
species show a preference for particular parts of the skin of the host, 
feeding only from the abdomen or legs ; others select the face, and 
especially the margins of the ears and eyelids ; only the females are 
blood-suckers. 

The larva consists of twelve segments, including the head. Each 

segment is contracted at both ends, and partly or entirely covered 

with spines or small protuberances ; eyes are 
Early Stages , ^ , . . \ . . 

absent. The antennae may be quite simple, consisting 

of a single unjointed spine-like segment, or of two or more joints. 
On the ventral surface of the first thoracic segment there is a leg-like 
appendage which consists of two pseudopods fused together ; its surface 
may be smooth or covered with spines, and it is furnished at its apex 
with simple or bifid hooks. The anal segment is armed w^ith two ob- 
liquely directed pseudopods, which are sometimes very short and fused 
together, and are always furnished with hooks. The larvae often have 
curious papillae on their dorsal surfaces, each of which may terminate in 
a single hair or a number of spines. These structures and the numerous 
long hairs are valuable taxonomic characters. In some forms, for 
example, Forcipomyia, the nymph has the remains of the larval skin 
attached to it, and in addition long hairs on its thorax and abdomen. 
The thoracic stigmata may or may not be prominent. 

The larvae of some species are found under the barks of trees, on 
and under decaying leaves and wood, and in sap which exudes from 
trees ; the majority, however, live in still or running water, especially 
where there is much algal growth, and where there are water plants, 
such as Bromelia. In Brazil Lutz has found the larvae of several species 
of Ceratopogon and Forcipomyia in crab holes, at the edges of mangrove 
swamps, and below the algal crust on the sand along the seashore. 



CERATOPOGON: PREDACEOUS SPECIES 161 



Kieffer divides the genus Ceratopogon into the following subgenera ; — 

1. Wings bare Atricopogon. 

Wings hairy, at least in the female 2 

2. Hind metatarsus longer than the succeeding segment ; or 

equal to it in the male, and longer in the female . . CeratOpOgon. 
Hind metatarsus shorter than the succeeding segment ; or 

equal to it in the female, and shorter in the male . Forcipomyia. 

There are some fifty or more species of Ceratopogon (sensu lato) from 
Europe, America, India, and Australia. Kieffer gives the following key 
to the six species of Ceratopogon (sensu restricto) at present recorded 
from India. It is not known whether they are blood-suckers or not. 

Indian Species of Ceratopogon 

1. Wings hairy 2 

Wings not pilose but with microscopical hairs .... indianus. 

2. Wings with a white spot at the extremity of third long vein .... 8 
Wings with one or two black spots . ....... 4 

3. Anterior metatarsus a little shorter than the second segment, 

two to three times as long as broad albosignatus. 

Anterior metatarsus much shorter than the second segment, 

a little longer than broad albonotatus. 

4. Wing with a black spot on the radial cell (base of the wing) ; 

anterior metatarsus equal to two-thirds of the length of the 

second segment ... ...... macrorhynchus. 

Wing with two black spots on the anterior border ; anterior 

metatarsus not half as long as the second segment ..... 5 

5. Mesonotum dull, of chestnut brown, with long and scanty 

hairs ; distal part of the fourth long vein without a stalk . decipietis. 
Mesonotum of a brownish black with a golden pubescence ; 

distal part of the fourth long vein with a stalk . auronitans. 
Ceratopogon (Atricopogon) indianus, Kief., from the Zoological 
Gardens, Calcutta ; C. albosignatus, Kief., from Rangoon in 
February ; C. albonotatus. Kief., from Calcutta ; C. macrorhynchus, 
Kief., from Calcutta ; C. decipiens, Kief., from Simla in May ; 
C. auronitans, Kief., from Lower Burma. 

Austen has recently pointed out that Ceratopogon (Forcipomyia) 
castaneus. Walk., is a common blood-sucker in Southern Nigeria. 
Major Lalor, I. M.S., has recently recorded from Burma a predaceous 

species of Ceratopogon which preys on Anopheles 

XT- 1. J ^ 7 77 • Ai Predaceous species 

fuligtnosus, A.karwart and A.ludlowt. About six per Ceratopogon 

cent of fuliginosus caught in houses were thus attacked, 

the flies adhering to the abdomen and neck of the mosquito ; some of the 

Ceratopogon contained blood, probably sucked up from the mid-gut of the 

mosquito. Dr. Stanton records another Ceratopogon which attacks 

Anopheles fuliginosus, A.karwari, and A.sinensis in the same way in 

21 



162 



MEDICAL ENTOMOLOGY 



Kuala Lumpur, Federated Malay States. In this case the flies were 
invariably attached to the ventral surface of the abdomen, and always 
contained blood. It is doubtful whether the presence of blood in the 
Ceratopogon is more than accidental; probably its true food is the body 
fluid of the mosquito, as in the case with other predaceous flies 
(Asilidae). The connection between these species of Ceratopogon 
and mosquito-borne diseases, such as malaria, is a very remote one. 

Genus Culicoides, Latrielle 

Minute midges ttsually measuring 7 mm., in length, sometimes 1.5 
mm., nearly always of a dark brown or black colour, sometimes brownish 
yellow rarely whitish. The antennae consist of fourteen segments, the 
first eight or ten being globular or ovoid in shape, the remainder usually 
elongated, especially in the male. The wings are hairy, either over 
the whole surface, or only in parts; the third long vein is either united 
to the first by a transverse vein, or entirely blended with it ; the fourth 
vein is either forked near the base, or towards the middle of the wing. 
The wings are often marked with dark spots and light clear circles in 
transverse rows of three, four, or more. The femora are not spined ; 
the hind metatarsi are longer than the succeeding joints; the claws are 
simple and of equal length, and in some species have spines at their 
bases. The empodium is rudimentary, and is never more than half as 
long as the claws. When at rest these midges are very like those of 
the genus Ceratopogon. 

About eighty species of this genus are recorded from various parts 
of the world. They have much the same habits and general appear- 
ance as Ceratopogon. The females bite man as well as animals, and 
both sexes are attracted to a light. One species C. kiefferi, Patton, 
which is common in Madras in the cold months, feeds only in the 
early morning, and is somewhat erratic in its habits ; it occurs in 
large numbers on cattle on one day, and is practically absent the 
next. Sometimes many will be found on one calf, while others in the 
same herd are free from them. The males are often seen in large num- 
bers on window panes, where they may be mistaken for * eye flies ' 
{Siphonella) , 

Culicoides kiefferi, Patton. Female (Plate XXXI, fig 1). Head, palpi 
and antennae light brown. Thorax light brown with a median dark 
band extending from the anterior end to about the centre, where it 
divides into two short branches. Abdomen light brown with faint 




163 



PLATE XXXI 



Figure 1. Culicoides kiefferi, S. x 30. 

Figure Z. Head of larva of same enlarged. 

Figure 3. Claws and empodium of hind leg of C. kiefferi. 

Figure 4. Last segment of larva of same showing the tracheal 

gills extruded. 

Figure 5. Larva of C. kiefferi. X 50. 

Figure 6. Pupa of same, x 50. 

Figure 7. {a) Hind leg : (6) Fore leg, of C. kiefferi. 

Figure 8. Antenna' of C. kiefferi, 3 . 



CULICOIDES: EARLY STAGES 



163 



bands and spots. Legs brown, fore metatarsus (Plate XXXI, fig. 7 b), 
equal in length to the three succeeding joints ; empodium (fig. 6) 
small and indistinct. Wing white, the surface clothed with fine 
hairs, and in parts with longer ones. There are two large dark 
brown spots, one about the centre of the costal border covering the 
entire third long vein ; the other, which is also on the costa, is nearer 
the apex of the wing ; there are in addition numerous lighter spots. 
The third long vein, which is closely adjacent to the first, is very 
pale and abuts on the costa about its centre ; the fourth vein 
bifurcates about the centre of the wing, and the fifth divides 
opposite to the extremity of the third vein. Length 1.5 mm. 

The eggs of C. kiefferi are small and ovoid in shape, and are 
deposited in a mass on green vegetable matter at the margin 
of running water. They hatch in three days and ^^^^^ stages 
the larvae burrow into the green matter. If one 
places some of this in water in a white dish, and breaks it up 
with forceps, they come out and are then seen swimming about like 
giant spirochaetes ; their rapid vibratile movements are extremely 
characteristic. 

The larva (Plate XXXI, fig. 5), consists of twelve segments (includ- 
ing the head), all of which are smooth and almost entirely devoid of 
hairs. Unlike the larvae of all the other species of Chironomidae, 
that of Ctilicoides has no pseudopods on the ventral surface of the 
first thoracic segment. The head (fig. 2) is well developed, and the 
eyes are kidney-shaped. The dorsal surface and sides of the head 
are furnished with several small hairs, the two most prominent ones being 
situated on the mid-frontal region. The antenna of the larva of C. kiefferi 
consists of a single minute segment with a small hair at its apex. 
The mandibles are stout curved rods of chitin, and are armed with 
two teeth. 

The first thoracic segment of the larva in some species has a single 
delicate hair on its ventral surface, and the anal segment is furnished 
with three or four simple hairs. The last segment (fig. 3) of C. 
kiefferi has four pairs of appendages which are deeply bidentate, and 
which can be extruded or withdrawn into the segment. These structures 
appear to correspond to the tracheal gills of other larvae. There are 
two long tracheal tubes which originate in the vicinity of the gills and 
give off numerous lateral branches as they pass forwards ; there are no 
true stigmata. 

The pupa (Plate XXXI, fig. 4), is very characteristic. Its surface 



164 



MEDICAL ENTOMOLOGY 



is almost entirely devoid of bristles, but it has well developed spines 
at the sides of the abdominal segments, and knob-like processes on 
their dorsal surfaces. There is a pair of long breathing trumpets 
which arise from the sides of the mesothorax, their stalks are very 
narrow and are armed with several small blunt processes. The trumpets 
end somewhat like those of the pupae of the Culicinae. There are, 
in addition, several protuberances with hairs and spines at their extre- 
mities, and minute processes on the thorax. The pupa, which never 
has the larval skin attached to it, anchors itself by two prominent 
terminal spines ; or it may float on the surface. The flies hatch out 
in three days. 

Lutz in a recent paper records having found the larvae of Culi- 

coides in a variety of situations. The larvae of several species were 

taken from crab holes on the margin of a mangrove 

Habitat of Early swamp, where they were living on the decaying 
Stages: Breeding , , ' , , , . . 

Technique food of the crabs. Other species were common m 

the salt water around the mangrove shrubs, as well 
as in the slimy matter at the edges of the swamps. In searching 
for the larvae in localities where the flies are common, green vege- 
table matter at the edges of streams should be collected and broken 
up in some water in a white tray ; if there are any larvae in it 
they will be seen swimming about in the water. They should be 
transferred to a watch glass containing water and some of the green 
vegetable matter in which they were found by drawing them up 
with a pipette. In two or three days the pupae will be seen 
floating on the surface of the water at the edges of the watch glass. 
The larvae sometimes lie motionless at the bottom of the glass ; these 
are not dead but are pupating, and will soon float up to the surface. 
The pupae should be transferred to a piece of moist filter paper and 
placed in a tube plugged with moist cotton wool. The flies, when they 
hatch, can be fed without difficulty on the shaved surface on the 
abdomen of a calf. Some specimens should be placed in two per cent 
solution of caustic potash for mounting, as this is the best way to 
study the structure of the legs. 

Genus Johannseniella, Williston 
(Synonyms Ceratoloph us, Kieffer ; Sphaeromyias, Stephens.) 

Allied to Ceratopogon and Culicoides. All the femora are without 
spines ; the hind tarsal joints may he hairy or spinulose in both 



FAMILY SIMULIIDAE 



165 



sexes, or hairy in one and spinulose in the other ; the claws are either 
equal or unequal in length, and are always simple in structure ; the 
enipodium is rudimentary. 

The habits of the mature insects of this genus are similar to those 
of the other blood-sucking Ceratopogoninae ; their early stages are 
unknown, but will most probably be found in the same localities as 
those of the other genera. 

One species J. strictonota, Kieffer, is described from Calcutta, but 
it is not known whether it is a blood-sucker or not. Neave records 
J. fulvithorax, Austen, from British East Africa ; it is believed to be 
a blood-sucker. 

Genus Haematomyidium, Goeldi 

Antenna unth fourteen segments, the last ones elongate; palpi with 
four segments, the second and third long. Wings with microscopical 
pilosity intermixed with long hairs ; venation similar to that of Culi- 
coides. Legs long, femora not thickened, and without spines; hind 
metatarsi about twice as long as the succeeding segment. 

This genus was formed by Goeldi for a midge, commonly found in 
the houses of the natives of Para, South America, by whom it is 
called ' murium '. According to Goeldi the female is a blood-sucker. 
A single species H. paraense, Goeldi, is known, but according to Austen 
it is a true Ceratopogon (sensu restricto), and is probably identical with 
C. phlebotomus, Williston. 

FAMILY SIMULIIDAE 

Small thick-set, hunch-backed flies, usually of a dark colour, with 
short stout legs. The head is semicircular. Eyes round or kidney- 
shaped, holoptic and with moderately large facets on the upper sur- 
face in the male, dichoptic and with smaller facets in the female ; 
ocelli wanting. Antennae short, cylindrical, and somewhat flattened, 
as long as or a little longer than the head, and consisting of ten joints. 
The two basal segments are distinct, but the remainder are more or less 
closely united. Palpi short, cylindrical, recumbent and incurved, consisting 
of four joints; the first short, the second and third equal in length, and 
the fourth longer and thinner; the palpi are as a rule longer in the 
female than the male. Proboscis short and stumpy, with well developed 



166 



MEDICAL ENTOMOLOGY 



labella. Thorax gently arched, and without a transverse suture ; scutell- 
um small. Abdomen cylindrical, broad, slightly ovoid and sometimes 
tabanid-like, consisting of eight segments, the first being the longest ; 
external genitalia of male concealed. Legs well developed, never very long, 
femur broad and flat; tibia usually with a terminal spur; metatarsus 
much longer than the succeeding tarsal segments ; the last Joint is small ; 
empodium rudimentary. The metatarsus is as a rule broadly swollen 
in the male. Wings large and broad, anterior veins thickened and 
spinulose, the remainder poorly developed and often almost invisible. 
The subcostal or auxiliary vein ends about the middle of the rosta ; 
the second long vein is wanting; the third arises from the first at its 
middle, and is forked ; the fourth is a little curved, and is forked close 
to the base of the wing. 

This family contains the single genus Simulium, Latrielle. Alto- 
gether there are about one hundred species, distributed all over the 
world. Roubaud (1906) suggested splitting the genus into two sub- 
genera as follows : — Eu-Simulium, in which the second hind tarsal 
joint is short in both sexes, is curved, and has a dorsal notch at the 
base. The pupa has a small number of respiratory filaments, an 
incomplete cocoon, and is solitary. — Pro-Simulium, in which the 
second hind tarsal segment is elongated, straight, and has no notch 
at the base. The pupa has a large number of respiratory filaments, 
a complete cocoon, and is found in company with others. 

The Simuliidae are well known in most parts of the world on account 
of the great annoyance, and at times serious damage, which they may 
cause. In Europe and in India they are frequently called ' sand flies,' 
a name better reserved for the species of the genus Phlebotomus. In 
America they are known as ' buffalo gnats,' or ' turkey gnats,' the latter 
from the fact that they readily attack these birds and other fowls. 
Both in America and in the 'southern parts of Hungary these flies are 
often the cause of serious loss to farmers and stock breeders. They 
appear in swarms, attacking domestic animals of all kinds, and so irritate 
them by their bites that they manifest the most violent signs of fear 
and distress, shaking themselves, lashing their tails, and even careering 
wildly about in their efforts to rid themselves of their tormentors. 
Cattle will at times immerse themselves completely in water in search 
of relief. Birds are not exempt from their attacks, as their American 
name implies, and are often so tormented that they are driven from 
their nests. The flies bite them about the head and eyes, but will also 



SIMULIUM : NORTH AMERICAN SPECIES 167 



crawl under the wings, and weakly birds often die from the irritation 
of the bites and from the loss of blood. Even human beings are not 
exempt, and in some parts of Brazil the species are so prevalent and 
troublesome at certain seasons, that the natives are compelled to keep 
fires burning in order to protect themselves. They are well known in 
the Amazon District as ' pium', and in South Brazil as ' barrachudo'. 
Fortunately they do not enter houses. 



Brunetti's Key to the Indian Species of Simulium 

1. Thorax black, at most with dull reddish brown tinge occasion- 

ally . , . , . 2 

Thorax distinctly reddish brown, with short reddish hair . rufithorax. 

2. Thorax with grey shoulder spots and a wide greyish band 

on posterior margin grisescens. 

Thorax ash grey with three narrow black stripes . . . striatum. 
Thorax without either grey shoulder spots or posterior bands .... 8 

3. Abdomen destitute of any sign of yellow hair i 

Abdomen with short bright yellow hair, or with long rather 

shaggy brownish yellow hair ......... 6 

4. Hind metatarsus much incrassated, nearly as long and large as 

the tibiae metatarsal is. 

Hind metatarsus not so conspicuously incrassated, distinctly 

less in size than the tibiae .......... .5 

5. Antennae wholly black. Length 2jmm. ..... griseifrons.* 

Antennae reddish yellow at base. Length Ijmm. . . . rufibasis. 

6- Abdomen with normal short very bright yellow hair. ..... 7 

Abdomen with distinctly longer, shaggy brownish yellow hair, senilis. 

7. Abdomen with at least the first two segments yellowish, or 

brownish yellow ; often several segments so coloured . indicum. 
Abdomen all black aureohirtum. 

Johannsen's Key to the North American Species of 

Simulium 

1. Ground colour of thorax and abdomen deep yellow . . . . . . 2 

Grey or black ; its hairs may be pale ........ 8 

2. ' Femora with black tip, length of fly 2 mm.' Mexico . . ochraceum. 
' Femora without black tips. Length 3 to 4'5 mm. Rocky 

Mountains fulvum, 

3. Hind tarsi with its basal joint partly yellow ; legs bicoloured .... 9 
Hind tarsi unicoloured ........... i 

4. Halteres dusky ; thorax not striped 5 
Halteres white or yellow ; the female with striped thorax and 

bifid tarsal claws .6 



* Simulium griseifrons, of which the female only is known, is probably S. inetatarsale, 
of which the male alone is recorded ; the broadly dilated metatarsus noted in the key is found 
in most of the males of the genus. < 



168 



MEDICAL ENTOMOLOGY 



5. Body black ; the female with dense yellow pile, her tarsal 

claws simple ; the male with dense hair on the legs, his 
tarsal claws trifid. The wing with its radius three branch- 
ed. Length 3 to 4. 5 mm hirtipes. 

' Body grey, legs reddish grey, feet black ; length 3 mm '. This 
is said by Mr. Coquillett to be the same as pecnaritm, 
Riley invenustum. 

6. Males, eyes contiguous ........ . . 7 

Females, eyes separated by a distinct line 8 

7- Thorax velvety black ; legs reddish with black tarsi. Length 
1. 5 to 2 mm. Compare here also bracteattmi (male) ' with 
legs wholly brown ' . . . ..... meridionale. 

Thorax brownish black ; legs usually pale ; tip of tarsi not 

black. Length 2 to 4 mm. pecuarum. 

8. Thorax with silvery white pubescence ; legs brownish black, 

covered with whitish hairs. A small variety (less than 
2 mm. long), from New Mexico has been named occidentale, 

Townsend meridionale. 

Thorax with yellow hairs ; legs reddish brown, covered with 

yellow hair ; tip of tarsi blackish pecuarum. 

9. Males, eyes contiguous . , 10 

Females, eyes separated ........... 20 

10. ' Mesonotum wholly velvet black ; grey spot on sides of the 

second, fifth, sixth and seventh segments of abdomen. 

Length 1.5 mm.' bracteatum. 

Metanotum striped, or with greyish or metallic reflections .... 11 

11. Dorsum of thorax with one or more longitudinal stripes .... 12 
Dorsum unstriped 14 

12. Thorax with four longitudinal stripes ; posterior margin white; 

abdomen black. Sex not given. Cuban species . . . quadrivittatutn. 
Thorax not so marked ........... 13 

13. Front and middle femora and tibiae wholly yellow ; centre of 

mesonotum with a black vitta, elsewhere grey. Length 

1"5 mm. Colorado species ....... griseum. 

Femora and tibiae wholly or partly brown iSa 

13a. ' Femora and front tibiae yellow, their apices brown ; middle 
tibiae brown, a yellow ring beyond the base, hind tibiae 
brown, the extreme base yellowish. Mesonotum marked 
with a narrow median and laterally with a very broad velvet 
black fascia.' Length 3 mm. New Mexico . . . virgatum. 
Front femora brown, tibiae brown on apical part . . .... 186. 

13 b. Mesonotum with two narrow grey stripes (sometimes quite 
indistinct) on a velvet black ground, in which there are 
scattered golden hairs ....... vittatum; 

' Mesonotum marked with a narrow median and slightly wider 

lateral black vittae.' Length 2'5 mm. Missouri . . glaucum. 

14. Anterior femora yellow. Mexican species ....... 13 

Anterior femora black 17 

15. Abdomen with the base of the second segment, and the sides 

of the third, fourth, and fifth yellowish white, tibiae fuscous 

black with yellow bases. Length 4 mm mexlcanum. 

Abdomen black 16 



SIMULIUM: NORTH AMERICAN SPECIES 169 



16. Metallic bluish black species ; middle portion of fore tibiae, 

base of middle and hind tibiae, base of first and second 
joints of middle and hind tarsi, whitish. Length 2 mm. . metallicum. 
Thorax fuscous and cinereous pollinose ; the humeri pallid, 
fore coxae pale, middle and hind ones dark ; femora pale at 
the base, black at the tip ; tibiae black. Length 3 mm. . cinereum. 

17. An oblique metallic streak extending inward from each hume- 

rus ; posterior part of the thorax metallic. Length 2 to 

2'5 mm. venustum. 

Humeral spots not metallic ......... 18 

18. Anterior coxae yellow; long hair on femora and hind tibiae; 

thorax velvet black with white pruinose margin (Greenland) reptans. 
Anterior coxae black 19 

19. Thorax velvet black, with oblique cinereous humeral spots, 

and usually two tiny metallic spots between them. Length 

3 to 4 mm pictipes. 

Thorax velvety black with two very narrow grey stripes and 
posterior margin ; hind tibiae usually yellow at the base, 
hair on legs sparse ........ vittatum. 

20. Thorax striped 21 

Thorax without stripes ........... 25 

21. Dorsum of thorax with four longitudinal lines, posterior margin, 

white pollinose ; abdomen opaque black. Cuban species . quadrivittattim. 
Not with four stripes ........... 22 

22. Dorsum of the thorax with five stripes, the outer ones spot- 

like, the intermediate ones clubbed at the ends ; abdomen 
with black fascia on each segment, produced posteriorly 
at the middle and the ends. Sometimes the last few seg- 
ments have only three or five spots ..... vittatum. 
Thorax with one or three stripes ......... 32 

23. With three stripes 24 

' With an indication of a darker median vitta ' (see 31) . . griseum. 

24. Small species, length about 1"5 mm. ' Abdomen silvery, 

third and fourth segments wholly brownish, sometimes 
with a median spot on each; legs yellowish, tarsi blackish 
or brownish'. Species from Texas ..... tamaulipense. 

Larger species 3 mm. or more in length ....... 24a 

24ff. Middle tibiae brown with a yellow ring beyond the base ; 

vittae of mesonotum brownish, the median vitta dilated 
posteriorly, wider than either of the lateral ones. New 

Mexico virgatum. 

Femora and tibiae greyish, sometimes quite pale, tips of tibiae 
black. Latero-dorsal thoracic stripes clubbed at the anterior 
end. Third, fourth, fifth, and part of sixth and seventh 
abdominal segments with velvet black fasciae ; centre of 
6, 7, and 8 greyish or dull brown pictipes. 

25, Abdomen without distinct black spots ....... 26 

Abdomen spotted 3 1 

26, Abdomen black, covered with long yellow pile ; legs yellow, 

the tips of the femora and tibiae, and all the tarsi except 
basal two-thirds of the hind metatarsi, brown . . . bracteatum. 

Abdomen nearly bare .......... 27 

22 



170 



MEDICAL ENTOMOLOGY 



27. Body grey or cinereous .......... 28 

Body brown or black .......... 29 

28. 'Body grey with a white milky lustre, especially the pleura 

and pectus. Legs tawny, femora and tibiae with irregular 
piceous bands, tarsi piceous. Length 2'5 mm. Hudson 
Bay Territory'. This is a synonym of vittatnw, Zett., 

according to Mr. Coquillett (1898) decorum. 

Thorax fuscous or cinereous pollinose, humeri pallid, pleura 
pale cinereous, scutellum pale at the tip ; abdomen blackish ; 
fore coxae pale, middle and hind ones cinereous ; femora 
pale at the base, black at tip ; tibiae black. Length 3 mm. 
Mexican species ........ cinereum. 

29. Abdomen somewhat shining, yellowish grey or whitish at the 

sides, and yellow at the base ; legs brown, tibiae and fore 
coxae white, tip of tibiae and all tarsi black. European 
species, also occurring in Greenland ..... reptans. 
Basal segments of abdomen opaque, distal fore segments some- 
what shining black or brown. Two long hairs at the tip of 

the first and third fore tarsal joints ........ 30 

30. Legs reddish yellow, tarsi black, except proximal half of 

middle and hind metatarsi which are light yellow. Length 
2 mm. (St. Vincent Island). This is a synonym of pulch- 
rum, Phil., according to Hunter ..... tarsale. 
Legs black, base of tibiae, first joint of middle and hind tarsi 
and sometimes base of femora yellow ; extensor surface of all 
the tibiae more or less whitish. A widely distributed and 
varied species ......... venustum. 

31. Length I'S mm. Front and middle femora and tibiae wholly 

yellow ; hind ones, except apices, also yellow. Colorado • griseum. 
Length 2 5 mm- Legs brownish black, distal part of femora, 
base of tibiae, and greater part of metatarsi light yellow. 
California argus. 

LuTz's Key to the Brazilian Simuliidae 

1. Multicoloured species, the halteres and legs never entirely 

black 4 

Uniformly dark species, only the hair whitish, the wings 

colourless ............. 2 

2. The white hair thick but hardly visible to the naked eye .... 3 
The white hair thick and clearly visible .... flavopubescens. 

3. A little more than medium size, entirely black, from high alti- 

tudes pernigrum. 

A little less than medium size, more of a chocolate colour ; not 

an aggressive species ....... hirticosta. 

4. Ground colour of thorax grey to black . . . . . . , 10 

Ground colour uniform 5 

5. The sides of the thorax uniformly coloured ...../ 6 
The thorax black and gold, the marking varying . . . varians. 

6. Colouring vivid ............ 8 

Colouring dull , . . . ■ 7 



SIMULIUM REPTANS 



171 



7. Thorax reddish violet or reddish, often with dark stripes ; 

claws not serrated ; species of large size .... scutistriatum. 
Thorax reddish brown ; tomentum clear frosty ; species of 

medium size pruinosum. 

8. Thorax orange coloured .......... 9 

Thorax red rubrithorax. 

9. Edges of the thorax, and anterior sides of fore tibiae white perflavum. 
Without any white ; thorax with delicate tomentum . hebeticolor. 

10. Thorax without mother-of-pearl markings in the middle . . . . 12 
Thorax with mother-of-pearl markings in the middle . . . . . II 

11. Two anterior and submedian subtriangular spots . . . incrustatum. 
Mother-of-pearl-like longitudinal stripes .... minusculum. 

(amazonicum). 

12. Tomentum golden to red ; somewhat diffusely metallic or 

white ............. 13 

Tomentum in small whitish tufts ..... orbitale. 

13 The scale-like hairs of tomentum in groups or arranged in 

lines .............. 1 4 

The hairs not arranged in any order . . . ... . . , 16 

14. The thorax without any clear edging . . . . . . . . 15 

The edging very clear ; the legs very dark above . . subnigrurrii 

15. Scutellum dark ............ 16 

Scutellum light brown often lighter ..... subpallidum. 

16. Large thick-set species with a dark silvery shimmer ; from 

high altitudes distinctum. 

Medium-sized species with a dull shimmer ; from ravines, very 

aggressive . . pertinax. 

17. Halteres externally reddish brown ......... 13 

Halteres golden, with five clear golden stripes on the thorax ; 

a medium-sized species auristriatum. 

18. Halteres not very darkly coloured . . . . . . . . . 19 

Halteres of a deep reddish brown ; claws serrated ; medium 

sized species infuscatum. 

19. Claws not serrated ; very small species .... exiguum. 
Claws serrated ; somewhat large species .... paraguayense. 



Simulium reptans, L. Johannsen gives the following translation 
of Schiner's description in Fauna Aiisfriaca. 

Male. ' Velvet black, dorsum of the thorax with a silvery white margin, 
' spot-like on the humerus, broadly interrupted in front ; visible only 
' in certain lights. Pleura also with a whitish reflection ; abdomen 
' with silvery white spots on the second and on the last two segments, 
' wanting in rubbed specimens ; the posterior margin of the first segment 
' with long and dense brownish cilia. Head black, face greyish white ; 
' antennae and palpi brownish black, the former more slender than is 
' usual with the members of this genus, with whitish reflections on some 
' parts. Legs dark brown ; front coxae yellowish, fore tibiae silvery white 
'outwardly; middle tibiae yellow at the base, hind tibiae likewise, though 
' in less degree, light brown,- with a whitish reflection ; -metatarsi of the 



172 



MEDICAL ENTOMOLOGY 



' hind legs yellowish at the base ; the hairs of the fore and hind femora, 
' and particularly on the extensor surface of the hind tibiae, conspicuous. 
' Halteres bright yellow ; wings purely hyaline, with delicate and trans- 
' parent veins, those of the anterior margin being somewhat thicker and 
' more conspicuous ; the wing surface with a golden brown reflection ; 
' the media not petiolate. The short, scattered hair of the thorax seldom 
' distinct, the colour of the legs variable in intensity.' 

Female. ' In colouring does not resemble the male in the least. The 
' ground colour is blackish brown ; the dorsum of the thorax covered with 
' a depressed yellow pile, on the margin with a whitish reflection, on the 
' centre with a greyish reflection, the pleura greyish white. Abdomen 
' somewhat shining ; on the sides whitish or yellowish grey ; on the venter, 
' at least at the base, in living specimens, yellow, which is continued 
' around on the dorsum in some specimens, usually not distinct in dried 
' specimens. Legs brown, usually paler than those of the male ; the 
' tibiae, with the exception of the tip, and the fore coxae whitish or 
' yellowish white, the tips of the tibiae and tarsi black, the basal half 
' of the hind metatarsi and sometimes also the extreme base of the 
' following joint yellowish. Front and face grey ; antennae and palpi 
' brown, the former paler at the base. In other particulars as with 
' the male. Length 2 to 3 mm.' 

Simiiliitm reptaiis is widely distributed throughout Europe, and is 
stated by Sambon to be the invertebrate host of the parasite (?) of Pella- 
gra. In this connection it is interesting to note that it is not found in 
the United States, in some parts of which pellagra is very prevalent. 

Sim III ill III iiidiciiin, Becker. A large black species (2^ mm.), with a 
dark thorax and abdomen, except the last segments of the latter, 
which may be yellow or yellowish brown. Femora and tibiae yellow 
on their basal halves and black at their apices. It is widely distributed 
in North India, where it is known as the ' Potu Fly ' ; it is recorded 
from Baltistan at an altitude of 10,000 feet. 

Siiniiliuin striatum, Brunetti (Plate XXXII, flg. 1). Thorax grey 
with a few golden hairs, and with three moderately narrow dark stripes 
commencing just behind the anterior margin, and fading away before 
the posterior margin is reached ; sides of thorax dull grey. Abdomen 
black. Fore tibiae dark brown, posterior tibiae yellowish on basal half; 
hind metatarsi pale }-ellow with a black tip. This species was origi- 
nally described from Ceylon. It is very common in Kodaikanal 
(6,000 ft.) South India, where it breeds in all the hill streams. Its egg, 
larva, and pupa are depicted on Plate XXXII. 



PLATE XXXII 



Figure 


]. 


Siiuiiliiiiii striatum, ? . X 16. 


Figure 


; 


Egg mass of same on a blade of grass. 


Figure 


3. 


Pupa of same, x 14. 


P'igure 


4. 


Larva of same. x 14, 


Figure 


3. 


Single egg of same, highly magnified. 


Figure 


6. 


Ventral view of head of larva of same, showing the 






mouth parts. 


Figure 


7. 


Dorsal view of same, showing antennae. 



PLATE. XXXII. 




SIMULIUM : EARLY STAGES 



173 



Simiilium damnosum, Theobald. Body of a uniform black colour, 
antennae and palpi black. Thorax dark with golden hairs ; abdomen 
black with short dark hairs. The metatarsi and first two tarsi of the 
fore legs are swollen. Larva large and of a dark colour, with a pig- 
mented patch at the sides of the first thoracic segment. Pupa with 
a bifid comb of tubes which do not project much above the cocoon. 
S. damnosum is the well-known 'Jinga Fly' of Uganda, and is widely 
distributed throughout Equatorial Africa. 

At certain seasons Simuliidae appear in swarms and attack 
animals and even man. They are generally met with in the vicinity 

of streams, especially where there are woods. They 

11 U i. 1 1 i.u uj .lu Bionomics of Simu- 

usuaiiy bite larger animals on the abdomen, either j.^^ 

near the scrotum or udders, or on the fore legs. 
Other favourite places are the inside and along the margin of the ears, 
and round the eyes. They are most active during the early part of 
the day, from sunrise till about 10 a.m., when they retire to rest on 
the under surfaces of leaves close to the ground. They begin biting 
again towards evening, and may continue to do so till late at night, 
especially during moonlight nights. When attacking man they often 
settle on the forehead, back of the neck and the ears, and cause 
considerable annoyance by trying to crawl into the eyes and nose ; 
they may also bite the ankles, even through stockings. The bite is 
sharp and stinging and causes considerable irritation. 

In 1795 Schonbauer described the early stages of the ' Columbacz 
gnat ', Simidiiim columbaczence, Schon., and drew attention to the 
remarkable fact that its eggs are laid on leaves, blades 
of grass, etc., under water, and that the larvae attach xxxl?*' 
themselves to any fixed object floating in the water ; 
when about to pupate they spin a cocoon on the support. The eggs 
(figs. 2 and 5) are small ovoid objects, somewhat yellowish in colour, 
usually more pointed at one end than at the other ; they are often 
distorted, and then project at one side. They are enveloped in a 
gelatinous substance, and are spread out in an uneven layer either 
on blades of grass or dead leaves, or on stones, etc., below the surface 
of the water, usually where it is running swiftly ; they never lay their 
eggs in stagnant pools. Some species oviposit only on stones, others 
on any support under the water, especially in places where it rushes 
rapidly round a bend. When about to lay her eggs the female crawls 
down to the edge of the water, inserts a part of her abdomen beneath 
the surface, and , deposits the eggs with their accompanying gelatinous 



174 



MEDICAL ENTOMOLOGY 



substance. They hatch in about three or four days, according to 
the temperature. The larvae at once attach themselves to the support 
by their posterior suckers, and can be seen waving about in the 
water. 

The body of the larva is cylindrical, gradually broadening out pos- 
teriorly in the shape of an Indian club ; in some species the increase 
in breadth is very gradual, while in others it is some- 

larva^and'pupa^ what abrupt, and thus gives the body a constricted 
appearance in the middle third. The colour varies 
somewhat, dark olive green being the predominant shade, and the 
one which harmonizes best with the leaf or other support to which 
the larva is fixed. The body is composed of twelve rather indistinct seg- 
ments, five of which usually form the dilated posterior end. On the 
ventral surface of the first thoracic segment there is a well developed 
forwardly-directed pseudopod, which represents two legs fused to- 
gether ; it is conical in shape, and is armed at its apex with a circu- 
lar row of short booklets or spines. When the larva is touched the 
anterior pseudopod retracts. 

On the last segment there is another pair of pseudopods joined to- 
gether to form a flattened, sub-cylindrical sucker, armed with a row or 
rows of booklets arranged in regular transverse series. True stigmata 
are wanting ; the tracheal tubes end on the ventral side of the suckers, 
where they join three short, cylindrical tentacles, the anal gills ; these 
finger-like processes, which may be simple or branched, can be retract- 
ed, but when it dies in still water, or when the larva is dropped 
into spirit, they are always extruded. The head is large, somewhat flat- 
tened, and almost rectangular in shape, with two black approximated 
lateral eye spots, the anterior of which is usually the smaller of the two ; 
the posterior is reniform in shape. The labium is broadly rounded off in 
front ; the antennae are long and attenuated, and consist of three joints. 
The first is very small and inconspicuous ; the middle, which is longer, is 
about half the length of the last. Situated directly behind the an- 
tennae there are two broad, somewhat flat arm-like processes, the 
feeding brushes, each furnished with a long fan-like fringe of dark 
hairs ; if the larva is examined with a lens when under the water, 
they can be seen to open and close in rapid succession, the long 
hairs whirling round and drawing in small objects towards the oral 
opening. When the larva is dropped into spirit, they spread out and 
can -then be -easily studied. - .: .- 
■ - T-h« - mandibles are ' stout blades of chitin, armed -with" short stifU 



SIMULIUM: EARLY STAGES 



175 



spines at their inner ends as well as long delicate hairs ; the max- 
illae are somewhat triangular plates of chitin, densely covered with 
hairs arranged in a tuft, and usually with one slender spine just below 
their apices. The palpi are short, consisting of three joints. The labial 
plate may be broad or narrow, and is armed at its anterior end with three 
to five or more teeth, the external ones usually bidentate ; these teeth are 
useful in identifying the species. The alimentary tract of the larva is 
a simple tube, at either side of which there are two long glands, which 
secrete the gelatinous substance from which the anchoring threads and 
the silken fibres of the cocoon are made. When the larva is about to 
pupate, it spins the characteristic case by first fastening a thread on one 
side of its support, and then carrying the other end over to the opposite 
side ; repeats the process until it has constructed a heart-shaped 
pouch, deeply scooped out at its anterior end, and pointed posteriorly ; 
this is attached by its sides to the support, which may be the back of 
a leaf or twig, or the surface of a stone. 

Miss Phillips has made some detailed observations on the spinning 
of the cocoon of Simiilium pictipes, Hagen, which she describes as 
follows : — ' In spinning, the thread issues from the mouth and is placed 
' in the different positions by the thoracic proleg. The head is bent 
' down, and with the proleg the thread is drawn around the body and 
' other threads placed or twisted in all directions, until a very irregular 
' network is formed, covering the whole of the body, except the head. 
' The skin of the head is then cast off, and the insect pulls itself out 
' of the skin of the body, leaving it whole. The cast skin may often 
' be found in the cocoon, with the pupa. The cocoons are commenced 
' at the upper margin and spun continuously down to the caudal end, 
' where several threads are drawn from the cocoon and attached to the 
* last one or two of the body segments of the pupa. The threads hold 
' the pupa very firmly, and are alwaj's found when the pupa is pulled 
' out of its case.' 

The larvae feed on small crustaceans, such as Copepods and Isopods, 
small polyps, fresh water sponges and small animalculae, which are present 
in all streams. Their movements are interesting to watch when crowded 
together on a leaf. When a larva sways too much to one or other side, 
and touches its fellow, both rapidly retract. They can crawl up their sup- 
ports with great agility, the loops being rapidly made. Before it moves 
the larva always fixes its thread to the support so that if it becomes 
detached it can crawl back in safetj- . 

The pupa (Plate XXXII, fig. 3) is ovoid in shape the anterior end 



176 



MEDICAL ENTOMOLOGY 



forming a broad transverse ridge, at the end of which the raised antennal 
sheaths can be distinguished. The thorax is gentl)' convex, and has 
attached to its lateral edges a tuft of from six to eight or more long 
filamentous hairs, or thick bifid processes, the thoracic gills. Each fila- 
ment projects freely from the open end of the pouch. The structure 
and number of the gills are useful taxonomic characters. The abdomen 
may or may not be furnished with spines, and usually has at the tip two 
bent or recurved hooks, b)' which it is anchored to the bottom of the 
pouch. At first the pupa is of a light mahogany colour, but it becomes 
slowl}' darker, until just before the imago emerges it is almost black. 

Bubbles of gas now begin to collect under the pupal skin, and, when it 
splits horizontally along the middle line, the fly rises to the surface in a 
bubble. It crawls on the water or is washed down for a short distance, 
but soon clings to some support, and then flies away and settles on some 
neighbouring twig or blade of grass. 

The essential factors governing the well-being of the larvae of Siiniiliiim 

are water in rapid motion, and a support on which to fix themselves. 

These conditions are always available in streams 
Breeding Technique • r i 11 * 1 i 1 , 

commg irom some elevated place. A sudden bend, 

a declivity, or any obstruction will cause an acceleration in the motion of 
the water. In such places blades of grass, dead leaves, sticks, and stones 
accumulate, and it is here that the larvae are found in large numbers. 
It is quite futile to attempt to breed out the flies by keeping the larvae 
and pupae in any kind of aquarium, for they are sure to die. Newstead 
states that he has bred out the imagines by placing the leaves, stones, 
etc., to which the pupae were attached in a glass jar covered with fine 
muslin netting, merely keeping them moist ; in some cases the insects 
hatched out of pupae which were quite dry. 

In attempting to breed Siimtlium, it is best to place some simple 
apparatus around the larvae in the water, and not to remove them to 
trays or dishes. A tin frame, similar to the top of the fly jars (see Chapter 
4 and Plate XLIV, fig. 5), should be fixed over the place where the 
larvae are attached, either by burying it in the sand, or tying it with 
string to some supports at the sides. When the larvae have pupated, a 
fine meshed net can be fitted over the frame, and in this way the water 
will still flow^ past the pupae, and the flies, which will hatch out under 
natural conditions, will settle on the net after rising to the surface. 
As the males are not blood-suckers they can seldom be obtained except 
by breeding them out. 

Lutz suggests another simple way of breeding Simiilium. A large 



FAMILY PSYCHODIDAE 



177 



lamp chimney is partially immersed in the water, horizontally and in the 
direction of the current, and the leaf or twig to which the larvae are 
attached is then passed into the chimney ; the water flows through the 
chimney, so that the larvae remain under natural conditions ; when they 
pupate the ends of the chimney should be covered with fine netting, 
which will prevent the flies from escaping. 

FAMILY PSYCHODIDAE 

Small to minute moth-like gnats xvith narrow depressed heads; frons 
wide in both sexes ; ocelli wanting. Antennae long, as long as the thorax 
and head together, with a beaded appearance, and thickly covered with 
hairs ; each antenna is usually composed of sixteen segments, the two basal 
ones being short and cylindrical . Palpi recurved, covered with hairs and 
scales, and consisting of from four to five segments. Proboscis very short, 
or as long as the head. Thorax raised, arched, and covered with dense 
hairs ; scutellum rounded. Abdomen cylindrical, composed of from eight 
to ten segments ; male genitalia prominent, consisting of two or three 
pairs of appendages ; in the female the ovipositor may be prominent or 
concealed ivithin the last segment. Legs stumpy, or very long and 
slender, covered with hairs and scales ; claws small. Wings large, oval 
or lanceolate in shape, covered with hairs or scales, when at rest either 
held in an arched manner over the abdomen, or in an upright position ; 
the margin is fringed with hairs. The costal vein is continuous round 
the wing ; the other veins are well marked, and are almost all longi- 
tudinal and hidden by hairs or scales. Subcostal vein very short. The 
second long vein arises near the origin of the first, and may be 
forked either once or twice ; the front vein, which is often spoken of as 
the second division of the second vein, is considered by some to be 
a branch of the third vein. In any case there appear to be either one or 
two simple longitudinal veins between the second and fourth. The vein 
(3rd) just anterior to the posterior forked vein (4th) nearly always 
terminates at or near the tip of the wing. The fifth and sixth 
longitudinal veins end at the border of the wing, and the seventh, 
if present, is always short. The cross-veins are very indistinct, and 
are situated in the basal half of the wing. The supernumerary and the 
mid-cross veins, situated at the base of the third long vein are the 
most prominent. The eggs of the Psychodidae are laid in damp earth, 
where there is green algal matter. The larvae are cylindrical, the last 
segment often ending in a. short stiff stigmatic tube. The -pupa 
23 



178 



MEDICAL ENTOMOLOGY 



resembles that of the Culicinae is inactive, and often has respiratory 
trumpets. 

The Psychodidae are small hairy moth-like flies, commonly known as 
' owl midges '. They are frequently seen in dark corners, on windows, or 
in damp decaying grass, and about horse and cowdung ; their flight is 
feeble, and is accompanied by a peculiar buzz. Nearly all the species are 
hairy, and hold their wings arched over the abdomen, except the Phle- 
botominae, in \\'hich the wings are raised above the body. As far as is 
known at present, only the genus Phlehotomus contains blood-sucking 
species, the well-known ' Papataci ' or ' Sand Flies '. These insects 
have attracted considerable attention during the last few j'ears on account 
of the connection of Phlebotomus papatasi, Scopoli, with Papatasi or 
Phlebotomus Fever. 

This febrile condition was described many years ago by Pym, an 
army surgeon in Malta, but it remained one of the obscure fevers of 
unknown origin until 1908 when Doerr studied it in Herzegovina. This 
observer proved that the infection was transmitted by P. papatasi, 
and Birt and others have since confirmed his work. It is now known 
as the result of actual transmission experiments in Malta, Crete and 
in London, that the fly is infective seven to ten days after ingesting 
the virus of the disease, which is present in the blood of a sick person 
during at least the first day of the fever. The disease is probably 
widely distributed, and is believed to occur along the North-West 
Frontier of India and in parts of South America. 

The family Psychodidae is usually divided into two subfamilies, 
the Psychodinae and the Phlebotominae, which may be distinguished 
by the following characters : — 

Subfamily Psychodinae. Owl-like midges denselj' covered with hairs. 
Seventh longitudinal vein without exception well developed. Second 
vein forked once, or, as some consider, twice ; the first division is then 
very near the base of the wing, the lower branch running out to the tip ; 
the upper branch again forks nearer the base than the middle of the 
wing. Proboscis short, not armed for piercing ; ovipositor strongly 
chitinized and ending in a pair of flap-like valves ; male genitalia con- 
sisting of two or three appendages. 

Subfamily Phlebotominae. Not such hairy moth-like flies. Seventh 
longitudinal vein entirely absent, or if present markedly reduced ; in 
a few instances it runs to the wing border. The second longitudinal 
vein forks about the middle of the wing, and the upper branch again 
divides nearer the tip than the middle of the wing. The proboscis 



GENUS PHLEBOTOMUS 



179 



in the genus Phlebotomus is longer, and is armed for piercing ; the 
ovipositor is hidden ; the male genitalia consist of three pairs of 
appendages. 

Williston's Key to the Common Genera 

1. Two simple longitudinal veins between the forked veins ..... 2 
One simple longitudinal vein between the forked veins ..... 5 

2. The first simple vein arises from the forked vein much beyond 

the anterior cross-vein ...... i . Phlebotoitius. 

(Phlebotominae). 

The first simple vein arises near the anterior cross-vein .... .8 

3. The second simple vein ends at, or near the tip of the win^ . Psychoda. 

(Psychodinae). 

The second simple vein ends distinctly beyond the tip of 

the wing Pericoma. 

(Psychodinae), 

4. The seventh longitudinal vein (the most posterior one) is not 

much shorter than the sixth ....... Trichomyia. 

(Phlebotominae). 
The seventh longitudinal vein is very short .... Sycorax. 

(Phlebotominae). 

Phlebotomus is often confused with Psychoda and its allies, but the 
following points will help to distinguish them : — 

Psychoda : small stumpy flies with short legs and bushy wings, 
Phlebotomus : more elongated and have longer legs and narrower wings, 
which are nearly always held away from the body. Should there still 
be any doubt, drop a specimen of the fly into two per cent caustic potash 
solution, clear it and mount it entire, or dissect off the head and 
mount it alone. In Phlebotomus the mandibles and maxillae are serrated 
and obviously formed for piercing ; in Psychoda they are poorly developed 
and not formed for piercing. 

Genus Phlebotomus, Rondani 

Small psychodids with relatively large hairy icings ichich are held 
upright, and are devoid of scales. Palpi of five joints, cylindrical 
in shape; according to Newstead the third palpal segment of some 
species is provided icith minute spines, probably of a sensory nature. The 
spines may be squamiform and icith short pedicels (P. minutus) or sapth- 
uliform and with long curved pedicels (P. papatasi). Antennae long and 
slender, consisting of sixteen segments, the first short and thick, the second 
rounded, the third the longest, and the remainder swollen at their proximal 
ends ; in some species several of the segments have geniculated spines 
(Newstead). Proboscis longer than the head, and conical in shape 



180 



MEDICAL ENTOMOLOGY 



Thorax covered with hairs. Abdomen with eight segments, narrow and 
thickly furnished withhairs. Male genitalia (Plate XVII, fig. 4) consist- 
ing of three appendages (see page 86). Female organs indistinct, forming 
superior and inferior leaf-like appendages, which are covered with hairs ; 
a true ovipositor is wanting. The second longitudinal vein is forked 
twice, once about the middle of the wing, and a second time at the outer 
third ; the first branch is spoken of in the above key to the genera 
as a simple longitudinal vein, which, with the third, lies between the 
forked veins. 

Newstead gives the following key to the Maltese species : — 

A. Abdominal hairs recumbent. 

[a) Integument black. Large species. Palpi with second 

segment longer than the third nigerrimus. 

(h) Integument ochreous. Small species. Palpi with second 

segment one-half the length of the third .... minutus. 

B. Abdominal hairs more or less erect. 

(a) Legs in both sexes relatively short, average length of hind 
leg, 3 mm. Terminal segment of superior clasper of 
male scarcely half as long as the inferior clasper . . perniciosus. 

(h) Legs in both sexes relatively long ; average length of hind 
leg, 4 mm. ; terminal segment of superior clasper of males 
slightly longer than the inferior clasper .... papatasi. 

Phlebotomus nigerrimus, Newstead. A black or brownish black species 
closely allied to P. papatasi, but with the hind margin of the wing 
strongly arched, and the sixth longitudinal vein short, ending about the 
centre of the hind margin of the wing. It is a rare species and only 
occurs in certain parts of Malta (Gozo) ; the male is unknown. 

Phlebotomus minutus, Rondani. A dull golden ochreous species of small 
size (1.5 to 2 mm.). The second palpal segment is about one-half the 
length of the third ; fourth segment shorter than the third ; fifth segment 
long and slender. The third antennal segment is relativel}- short ; the 
hairs on the abdomen are recumbent. It is very active in captivity, leap- 
ing about, and whirling round, and according to Newstead it can be 
distinguished from all the other Maltese species by this habit alone. 
Marett states that it breeds in the rubble walls, bastions, and ground 
ventilators in Malta. 

Phlebotomus perniciosus, Newstead. A somewhat dark species with or 
without a reddish brown spot on the thorax ; it is smaller than papatasi 
with which it may be confused. Its legs are also shorter, and the male 
genitalia are smaller. The female is darker than that of papatasi. It is 
widely distributed in Malta, and is ver}- common during July, August, and 



PLATE. XXXIII. 




PLATE XXXm 



Figure 1. Egg of Phlebotomiis papatasi, much enlarged, to show 

the reticulated surface. 
Figure 2. Plileboioniiis papatasi, 3 , enlarged about 20 times. 
Figure 3. First instar of larva of same enlarged. 
Figure 4. Phlebotomus papatasi, ? , enlarged about 20 time*. 
Figure 5. Pupa of same showing larval skin attached, enlarged. 

All the above after Newstead. 



PHLEBOTOMUS PAPATASI 



181 



the early part of September. According to Marett it has the same breed- 
ing habits as miniitiis. 

Phlebotomiis papatasi, ScopoH (Plate XXXIII, figs. 2 and 4). A pale 
yellowish grey species, sometimes with a dark coloured fringe to the costa 
and the hind margin of the wing. The external genitalia of the male 
are much larger than those of any of the other Maltese species, as can be 
readily seen with the aid of a hand lens. The wing is narrower, but 
the posterior margin is more distinctly arched than the anterior. It is 
larger than its near ally peniiciostts, paler in colour, and has longer legs. 
This species is known to transmit the parasite (?) of Phlebotomus Fever. 
It is widely distributed in Southern Europe, North Africa, and the whole 
of North India. According to Marett in Malta, it breeds in caves and 
embankments. 

Annandale and Brunetti's Key to the Indian and Cingalese species 

1. The second longitudinal vein forks nearer the middle of the 

wing than at one-fourth. Petiole of first submarginal cell 
always much longer than one-third of the cell's length, except 

in /it«fa/a_Ve»s/'s, in which it forks exactly at one-third • • . . 2 
The second longitudinal vein forks exactly at one-third of the 
wing. Petiole of first submarginal cell only one-third as long 
as the cell . ■ .... 8 

2. Tip of first longitudinal vein, either about half-way between 

fork of second vein and tip of wing, or nearer tip of wing. ... 8 

Tip of first longitudinal vein distinctly nearer fork of second 

vein than tip of wing 3 

3. Fork of upper branch of second longitudinal vein nearer fork 

of second vein than tip of first vein. Wing comparatively 
lanceolate ; fork of second vein beyond that of fourth vein. 
Colour of insect yellowish grey. Genitalia of male with 

three chaetae at tip himalayensis. 

Fork of upper branch of second longitudinal vein nearer tip of 

first longitudinal vein than fork of second vein ...... J 

4. Wing broader ; fork of second vein before that of fourth vein. 

Colour of insect dark greyish brown. Genitalia of male with 
both the middle chaetae median. Hind femur between one- 
half and three-quarters as long as its tibiae, and distinctly 
longer than the metatarsus, which is shorter than the rest of 

the tarsus. Length 2i mm. perturbans. 

Wing lanceolate ; fork of second vein and that of fourth \'ein 
practically opposite one another. Colour of insect silver 
grey. Genitalia of male with the middle chaetae subapical. 
Hind femur nearly as long as its tibia, more than twice the 
length of the metatarsus, which is shorter than the rest of 
the tarsus. Length IJ mm minutus. 

5. Fork of upper branch of second longitudinal vein barely before 

tip of first longitudinal vein (not a reliable character). Sides 
of thorax conspicuously paler than the dark dorsum. Genita- 
lia of male with two chaetae at tip and three median ones. 



182 



MEDICAL ENTOMOLOGY 



Hind femur less than half as long as the tibia, distinctly 
shorter than the metatarsus, which is longer than the rest 

of the tarsus argentipes. 

Fork of upper branch of second longitudinal vein some little 
distance before tip of first longitudinal vein. Thorax more 
uniformly concolourous 6 
6- Length 3 to 3|- mm. Wings comparatively broad. Colour of 
. insect grey. Genitalia of male with two chaetae at tip and 

three median ones major. 

Length 2 J mm. Wings narrower or moderately broad ..... 7 

7. Wings narrower. Colour of insect yellowish grey. Genitalia 

of male with three chaetae at tip and two median ones. 
Hind femur between one-half and three-quarters as long as 
the tibia, and nearly twice as long as the metatarsus, which 

is shorter than the rest of the tarsus papatasi. 

Wings moderately broad. Colour of insect rather dark brown. 
Hind femur about half as long as its tibia ; equally as long as 
the metatarsus, which is equal in length to the rest of the 

tarsus (the male is unknown) argentipes, vari- 
ety marginatum. 

8. Length 2^ mm. Wings purplish irridescent. Genitalia of 

male with four chaetae (2 apical, 1 subapical, 1 median) malabaricus. 
Length 3 mm. Wings uniformly pale brownish grey. Genitalia 

of male with five chaetae (2 apical, 3 median) . . . zeylanicus. 

Phlebotomus himalayensis, Annandale. A yellowish grey species re- 
sembling minittus in general appearance, but distinctly larger and yel- 
lower ; the wing is easily distinguished by the length of the anterior 
branch of the second longitudinal vein. It is found in the Himalayas 
between the altitudes of 4,000 and 7,000 feet, and is common during May, 
June and July. 

Phlebotomus pertiirbans, Meijere. A dark brown species abundant in 
the jungle hills at the base of the Eastern Himalayas ; it is also found 
in Java. 

Phlebotomus minutus, Rondani. (P. babu, Annandale.) Probably the 
same as the European form, but according to Annandale it is of a silvery 
grey colour. It is the smallest of the Indian species, and can be distin- 
guished from argentipes by its narrow wings and uniformly greyish 
colour. It is widely distributed all over India, and is common in Ceylon; 
but is not found at high attitudes. In Madras it is common in June and 
July, and sometimes in September, especially after small showers of rain, 
but it entirely disappears during the south-west monsoon and is never 
seen during the cold weather. 

Phlebotomus argentipes, Annandale and Brunetti. Thora.x dark 
brown or even blackish, sides yellowish, a character by which it can be 
easily distinguished from all the other Indian species. It is widely 



PHLEBOTOMUS: INDIAN AND AFRICAN SPECIES 183 



distributed along the east coast of India, and is also found in parts of 
Ceylon. Annandale states that it has the habit of biting the ankles 
under a dinner table. A variety of a lighter colour, named by him margi- 
natits, is also said to occur in Ceylon. 

Phlebotomus major, Annandale. Allied to argentipes but distinguished 
by its larger size, uniform golden colour, more elongate tarsi, and b}- the 
characters of the male genitalia. It is found all along the outer Himalayas 
from the base to 8,000 feet above sea level. A variety ^r/s^a, Annandale, 
is recorded from Kurseong in the Darjeeling district; it is greyish or 
brownish and not of a golden colour. 

Phlebotomus malabaricus, Annandale. This species is closely related 
to pert II rba lis, and is found in the jungles at the base of the Western 
Ghats. 

Phlebotomus zeylanicus, Annandale. Thorax and abdomen brown. 
Wing venation characteristic, but resembling that of malabaricus and 
himalayensls. It is recorded from Peradenyia, Ceylon. 

According to Annandale P. papatasi is widely distributed in North- 
West India, and is found as far east as Pusa in Bihar. In Chritral it has 
been associated by Wall with a form of fever resembling Phlebotomus 
Fever. 

The following species are recorded from Africa : — 

Phlebotomus ditboscqui, Neveau-Lemaire. A species related to j^tr/xT^crs/ 
but differing in its darker colour, smaller size, and shorter proboscis. 
The antenna in the female is said to consist of thirteen segments — an 
unusual number in the genus — and the apical joint is shorter than the 
preceding one. Newstead appears to be doubtful as to whether it is 
distinct from papatasi. It is found in the French Soudan. 

Phlebotomus antennatus, Newstead. This species can be distinguished 
from most of the other Phlebotomi by the structure of the antennal 
joints, which are short and stout, the third to the thirteenth being more 
bead-like than in the case of any of the other species. According to 
Newstead, it is distinguished from P. minutus, variety africanus, hy its 
stouter and shorter legs. It is found at Salagoa on the Gold Coast. 

Phlebotomus squamipleuris, Newstead. A small species, which may 
be mistaken for P. papatasi, but is distinguished from it by its narro\\ er 
wing, and by the fact that the pleurae are clothed with large flat 
scales like those of mosquitoes. It is found at Khartoum in the Soudan. 

South American species of Phlebotomus. 

Lutz and Neiva, in a recent number of the Memoirs of the Oswaldo 



184 MEDICAL ENTOMOLOGY 



Cruz Institute, have described the South American species of the genus 
Phlebotomtis ; most of them were taken in uninhabited regions, particu- 
larly in forests where bamboo-inhabiting mosquitoes were plentiful. 
For the determination of the species they note that the relative lengths 
of the segments of the palpi afford valuable taxonomic characters in both 
sexes. They give the following key to three species : — 



Scales absent on the abdomen . . . . 
Scales present on the abdomen between the hairs 
Last palpal joint longer than the others 
Last palpal joint shorter than the second or third . 



2 



squamiventris. 

longipalpis. 

intermedius. 



Phlebofomiis rostra ns, Summers. This species is distinguished from 
the above by the great length of its head and proboscis, which in the 
female, taken together, are half the length of the rest of the body. It is 
recorded from Rio Javary. 

The bite of the sand fly is well known to everybody who has 

experienced it ; the stealthy \\ay in which it enters a mosquito net, 

either through the meshes, or bv crawling under the 
Bionomics ..." 

curtam, or even by passmg m between the mattress and 

the framework of the bed, make it a hated pest. The intolerable 
itching produced b}' the bite, and the stinging nature of the bite it- 
self, are diagnostic of the presence of these flies. Some people, how- 
ever, are in no way affected hy it. The hands, the wrists, the 
dorsum of the feet, and the ankles are the favourite sites in which they 
bite ; the face is also sometimes attacked. If a light is kept close to 
the bed fewer will enter the net. 

According to Marett, Phlebofoiiiiis in Malta does not fly long distances, 
about twenty yards being the limit of range of flight. If a strong 
wind is blowing they are onlj' seen in very small numbers, but when the 
wind dies down they reappear and their presence becomes ver}- noticeable. 
During the daj'time they are to be found in dark corners, among 
dark clothes, recesses in cupboards, behind pictures and similar places. 
The dark bathrooms of Indian houses are favourite resting places, where 
they will bite even in the middle of the day. 

In Malta Newstead notes that certain places were heavily infected 
while in others hardly any flies could be found ; the same has been 
observed in Madras, for some houses have large numbers, while others 
close bv are entirely free. Newstead attributes this localization to some 
unkno\\ n conditions which favour the breeding of the flies. 

In Malta Marett has found the flies resting in caves and embankments, 
and in cracks in walls where the surface pointing has fallen a\yay. 



PHLEBOTOMUS: EARLY STAGES 



185 



and where large crevices are left into which thej' can pass. The females 
are most active on still sultry nights, and then as they become replete 
with blood they cannot readily pass through the meshes of the 
ordinary mosquito netting. The males, if present, nearly always escape. 
When trying to catch one of these flies it will be noted that they make 
short leaps like the hop of a flea. 

Only the females suck blood, but Marett notes that both sexes may be 
seen burying their mouth parts in organic matter. The same observer 
states he has seen female sand flies, replete with fresh blood, coming 
out of a hole in a wall, and suggests that they had probably fed on rats. 

The breeding grounds of any species of Phlebotomtis are extremely 

difficult to locate. The small size of the larvae, their colour, and the places 

in which they are likely to be found, all increase the 
^.^^ , . ^ . . . , Early stages 

dirhculties. It is mterestmg to read even Newsteads 

account of his efforts in this direction in Malta, in which he only found 

a few larvae after prolonged and repeated search. In spite of the 

difficulties the worker should always endeavour to locate the 

breeding grounds of any species of Phlebotomtis, as all information 

will prove of the utmost value to other workers in the same field, 

Grassi found the larvae of P. papatasi in all kinds of damp refuse in 
cellars, and particularly on the sides of drains where water splashes or 
trickles down. In Malta, Newstead found the larvae in caves, and in 
crevices and fissures under loose rocks where there was some damp 
earth ; they were at some distance from the surface. They were also 
found low down near the foundations of stone walls, and on the under 
surfaces of stones. In all these places there was organic matter of all 
kinds, chiefly the excreta and remains of insects, wood lice, etc., as well 
as sufficient moisture and absence of light. It should be noted that, as 
Newstead points out, the larvae of Phlebotomtis have the habit of 
flicking themselves off the surface of the stone or other object when 
exposed to light, and are easily lost. The pupae are the most difficult 
to detect, as their colour harmonizes with their surroundings. 

Marett reports having found the larvae in wells, latrines, tanks, venti- 
lation shafts and manholes, but the chief breeding places in Malta, 
according to this observer, are stone walls which are dry above ground 
level, but moist below the surface. 

Hewlett found larvae in the following situations at Pusa, Bengal : — 

1. The nearly dried mud of a cement channel, leading from a well 
reservoir. 

2. A small heap of kitchen refuse near the base of a wall. 

24 



186 



MEDICAL ENTOMOLOGY 



3. The damp earth between some bricks, forming a small platform 
for a sacred plant in the courtyard of a house. The bricks in this case 
were more or less covered with algal growth, and among them were ants, 
the larvae and nymphs of wood lice, the larvae of Mycetophilidae, and 
other small creatures, 

4. Among the bricks and tiles in a small heap of earth and rubbish, 
where 'the conditions were similar to those mentioned above. 

5. The damp leafy matter taken from the earthy sides of an open 
reservoir where water from several gutters accumulated ; the gutters, 
which led from houses, were of cement and contained much nitro- 
genous matter. 

Howlett also suggests that in India the nests of termites may be places 
where sand flies breed, for the adult insects have been seen in the 
surface galleries. 

Newstead has observed the method of oviposition of Phlebotomus in 
captivity, and notes that the fly assumes a curious attitude ; it lowers its 
proboscis, crosses the middle and hind pair of legs behind the abdomen, 
which is then elevated and extended to the full ; the egg is then shot out 
to a distance equal to about three times the length of the abdomen. 

The egg (Plate XXXIII, fig. 1) is translucent when first laid, and is 
covered with a thin layer of viscous substance ; five hours later it 
assumes its normal colour. Newstead describes it as follows: — ' Form 
very elongate, dark brown, shining, with longitudinal black wavy lines, 
which in certain lights give the periphery of the egg a faintly rugose 
appearance ; these black lines are slightly raised, and are joined by slender 
cross lines so that a faint but rather coarse reticulation is formed. 
The transverse lines are, however, very diflicult to trace unless they are 
illuminated by a strong beam of light.' The incubation period lasts 
about nine days. 

The larva (Plate XXXIII, fig. 3) is cylindrical and like a small cater- 
pillar. It has a dark head, greyish white body, and long caudal bristles. 
The antenna consists of three segments, the two basal ones rudimentary, 
the third broad and flat, and armed with a centrally placed hair. It 
has black caudal bristles arranged in two pairs ; each inner bristle is 
almost as long as the body, while the outer ones are shorter. 

The pupa (Plate XXXIII, fig. 5) is ochreous buff, with a curved ab- 
domen and a triangularly shaped head. The front view of the head 
resembles that of a ram in miniature, the long antennal sheaths, curving 
behind the eyes, simulating the horns. The larval skin, at least in 
P. papafasi, is always attached to the two distal abdominal segments, a 



FAMILY CULICIDAE 



187 



condition which is also seen in the larvae of some Chironomidae 
(Forcipoinyia) . 

In order to breed out Phlebotomiis from the egg a number of replete 

females should be caught and kept in a large test tube together with 

some moist filter paper ; the mouth of the tube should 

, . , . f ,. 11 Breeding technique 

be covered with a piece of muslin and not with the 

ordinary mosquito netting. Males, if they can be caught, should be 
kept with the females and the tube placed in a cupboard. When the 
eggs are laid they should be transferred with the aid of a fine brush 
to some moist organic matter such as the remains of an insect ; if 
they adhere too firmly to the filter paper, the piece should be cut out. 
It is sometimes possible to raise a few flies in this way, but the task 
is not an easy one and requires constant attention. 

Marett has successfully bred out P. papatasi in a test tube on the 
sides and the bottom of which be placed the excreta of lizards and 
wood lice, first moistening it with water. After the flies had paired the 
females were transferred to the prepared test tubes, and were fed as soon 
as the previous meal had been digested. After the eggs were laid, 
the tubes were kept moist by daily adding a drop of water, and by 
wetting the cotton plug. The larvae hatched in from six to eight 
days, and were then transferred to a petri dish by filling the tube 
with water, which was then poured on to filter paper cut to fit the 
dish. The larvae float and later come to lie on the excreta. It is 
important to avoid an excess of moisture. 

FAMILY CULICIDAE 

Slender Nematocera with either a long forwardly directed proboscis 
adapted for piercing in the female, or with a slwrt proboscis. The head 
is small and spherical in shape; the eyes are reniform ; ocelli 
wanting. The antenna is slender and is composed of fourteen or fifteen 
joints, the basal one being globular, and either bare or hairy ; the re- 
maining segments are covered with hairs ; it is plumose in the male, and 
pilose in the female. The thorax may be arched, and there is no 
transverse suture. The scutellum is narrow, and may be unilobed or 
trilobed. The metanotum may be hidden, or visible, when it is usually 
arched. The abdomen is elongated and somewhat flattened, and is 
composed of eight or nine segments; the male genitalia are prominent, 
and the ovipositor is short. The legs are long and slender, the coxae 
comparatively short, the tarsi- are elongated, ^td the -cldws footlved- in the- 



188 



MEDICAL ENTOMOLOGY 



male, but rarely with more than two serrations. The wings are long 
and narrow, and when at rest folded flat on the abdomen ; the venation is 
characteristic and constant; six longitudinal veins are nearly always 
present, the second, fourth and fifth ■fire forked ; the third is simple and 
arises from the anterior cross-vein about the middle of the wing; two 
basal cells are nearly always present. The veins are clothed with hairs 
or true scales, and the hind margin is fringed with scales or simple hairs. 

At present the family Culicidae contains about 1250 known species 
distributed all over the world. 

The Culicidae, like many of the other families of the Diptera, contains 

species which show minor differences in structure, the value of which 

is a matter of dispute. Dipterologists, however, have 
Classification of the , ^ ^ ^ ■ ^ ur i- r^u 

Culicidae been content to recognize two subfamilies of the 

Culicidae, the Corethrinae in which the proboscis is 

soft and not armed for piercing, and the Culicinae in which it is long 

and is, at least in the female, armed for piercing. 

The blood-sucking habit of the female mosquito, and the relation of 
certain species with the transmission of the parasites of malaria, yellow- 
fever and filariasis, have stimulated the study of these insects, with the 
result that workers of all nationalities have collected them from all parts 
of the world. In order to facilitate this study and to make the work of 
others accessible, Theobald has written an exhaustive monograph of the 
group, in five volumes, classifying them according to the structure and 
position of the scales on the various parts of their bodies. In Volume I 
of his work, The Culicidae of the World, he recognizes six subfamilies 
of the Culicidae, of which the Corethrinae is one, and this grouping is 
retained in Volume III published in 1903. In 1905 Eysell published a 
paper in which he suggested the separation of the Corethrinae from the 
Culicidae, raising them to family rank ; the family Culicidae being retained 
for mosquitoes alone. Theobald in Volume IV of his monograph, pub- 
lished in 1907, following this suggestion, divided the family Culicidae 
into ten subfamilies and more than one hundred genera, many of which 
are subdivisions of the older genera. In Volume V, published in 1910 he 
retains this classification but adds several new genera. 

Dipterologists have taken exception to this classification. Williston, 
for instance, points out that scale characters are highly artificial, and 
that a genus of mosquitoes cannot be raised to family rank without 
raising all other genera of equal rank in a like manner. Whether the 
classification based on the characters- of the scales, resulting as it has 



SUBFAMILY DIXINAE 



189 



in the multiplication of genera, is a natural one or not it is impossible 
to say. Theobald maintains it is the best method of grouping these 
insects, as it is simple and can be used by medical men and others in 
determining the species in the field. It must be said, however, that 
culicidologists themselves do not appear to be agreed as to the species 
which belong to many of the genera. 

The separation of the Corethrinae from the Culicidae is cer- 
tainly a retrograde step, for although it is true that the former are 
devoid of a biting proboscis, in other respects, especially in venation, 
they agree exactly with the Culicinae. No better parallel example could 
be given than the Stomoxydinae, (Stomoxys, Stygeromyia, Haematobia, 
Haematobosca, Bdellolarynx and Lyperosia) in which the proboscis is very 
different from that of Musca, yet Stomoxys and Miisca unquestionably 
belong to the family Muscidae, the two being linked together by the 
genus Philaematomyia. So also many of the Pangoninae, to take another 
example, have non-biting proboscides, yet they are placed by all diptero- 
logists in the family Tabanidae. 

According to Williston and others the Dixidae, which show many 
culicine affinities, should be included as a subfamily of the Culicidae, 
which is then constituted as follows : — 

Synopsis of the family Culicidae 

Proboscis projecting somewhat, not adapted for piercing ; 
entire insect almost devoid of hair and scales, especially the 
antennae in both sexes ....... 

subfamily Dixinae. 

Proboscis short, not adapted for piercing ; entire insect hairy, 
the antennae plumose in male and pilose in female 

subfamily Corethrinae. 

Proboscis much longer than the head, firm and well adapted 
for piercing in the female ; head, thorax, abdomen, legs and 
. .. wings, except in some species, covered in parts or entirely 

with scales .......... 

subfamily Culicinae. 

SUBFAMILY DIXINAE 

Slender Nematocera, almost devoid of hairs. Eyes round and dichop- 
tic ; ocelli wanting. Antennae elongated, basal joint globular, the 
remainder of varying length and size, the terminal ones almost filiform ; 
palpi four-jointed. Thorax arched, without a transverse suture ; 
scutellum unilobed and transverse, metanotum arched. Abdomen long 
and slender, consisting of eight segtnents, pointed in the female, and 



190 



MEDICAL ENTOMOLOGY 



thickened posteriorly in the male. Legs long and very delicate ; tibiae 
without terminal spurs. Wings well developed ; the subcostal vein ends 
about the middle of the wing; the second longitudinal arises from 
the first, also about the middle of the wing, and appears to be the 
commencement of the third vein ; it then arches forwards, and divides 
into two ; the fourth longitudinal vein is also forked. The seventh vein 
is rudimentary. There are four posterior cells, bid the discal cell is absent. 

This group, the members of which are confined to the single genus 
Dixa, Meigen, can be recognized by their large wings, distinct and 
characteristic culicine-like venation, and their long filiform, almost bare 
antennae. They are usually treated as a family, and are regarded as 
being intermediate between the Tipulidae and the Culicidae. The char- 
acter of the venation, the presence of the basal globular joint to the 
antenna, the larger size of the claws of the fore and mid-legs in the 
male, and their serration, are all points which link the Dixinae with the 
Culicinae. 

The larva of Dixa was studied by Reamur in 1714, and later by 
de Gear and Meinert, the latter depicting its structure in detail, as well 
as that of the pupa. The larva consists of twelve 
Early stages segments, and is bent at the fifth and sixth in the 
shape of a syphon, so that the head and anal end almost meet ; in this 
characteristic attitude it rests at the surface of water. On the ventral 
surfaces of the fourth and fifth segments there is a pair of pseudopods 
armed with hooks, and on the eighth, ninth and tenth there are a num- 
ber of stiff spines grouped together. There is a respiratory cup on the 
last segment, a terminal spine with three bristles, and two lateral 
processes armed with long or short hairs ; in some species the fifth to the 
tenth segments inclusive are furnished with shields bearing spines. 
The larva is found in shady pools containing weeds and algae, and 
as it is often of a dark brown colour, it may be easily overlooked. The 
pupa, which is almost black, lies motionless at the surface of water with its 
abdomen bent up under its thorax. It has a pair of respiratory trum- 
pets just behind the head. 

Four species of Dixa have been described by Brunetti as occurring in 
the Himalayas ; Adie records a species from Lahore. 

SUBFAMILY CORETHRINAE 

Slender Nematocera with densely hairy bodies. Eyes kidney-shaped 
and dichoptic ; ocelli wanting. Antennae long, markedly plumose in the 



CORETHRA: EARLY STAGES 



191 



male and pilose in the female; the first segment is globular. Palpi 
four-jointed and reclining downwards. Proboscis very short, concealed, 
and not formed for piercing. Thorax arched and projecting somewhat 
over the head. Sciitellitm simple, never lobed ; metanotum arched. 
Abdomen long and slender, consisting of eight segments. Legs long and 
delicate, always hairy, and tibiae without spurs. Wing venation 
typically culicine, scales only present on the wing fringe, and a few 
of the veins, otherwise the wing surface is hairy. 

The genera of the Corethrinae may be recognized by the following 
table modified from Williston's key : — 



1. Metatarsus shorter than the following segment , . . Corethra 

(Mochlonyx). 

Metatarsus longer than the following segment ....... 2 

2. Large species (10 mm. or more long) with true scales on cross- 

veins and with bifid claws Pelorempis. 

Small species, claws simple . . . . , . . 3 or 4 

3. Antennae with second segment long, spaces between verticils 

bare, true scales on distal parts of veins .... Ramcla. 
Antennae verticillate, veins devoid of scales, and only clothed 

with hairs Chaoborus. 

(Sayomyia). 

4. Antennae with second segment long, spaces between verticils 

hairy Corethrella. 

Antennae with second segment short, spaces between verticils 

bare Eucorethra. 



There appears to be some confusion regarding the synonomy of the 
Corethrinae. The species which Lichtenstein (1800) named Chaoborus 
antisepticus was only described in its larval stage, and it remains an 
open question as to whether it was a true Corethra (C. plumicornis) 
or not ; in any case, it seems a pity to change the well established and 
familiar name Corethrinae to Chaoborinae, as has recently been 
suggested by Edwards. 

The larva of Corethra is common in pools and ponds in Europe, and 
is a well-known natural history object ; it is almost transparent, 
and has been aptly named the ' Phantom larva'. It 
lies horizontally extended on the surface of the 
water, now and then suddenly whisking its posterior end and darting 
after its prey, for it is predaceous. Its head is pointed anteriorly ; 
antennae project over its mouth, and are armed at their extremities 
with five long curved bristles. When not in use they are flexed on 
the basal joint. The labrum is long and keel-shaped, and the mandibles 
are armed with several strong teeth. It preys chiefly on small larvae, 



192 



MEDICAL ENTOMOLOGY 



which are caught by the antennae and crushed between the mandibles. 
The larva has no stigmata ; the tracheal tubes have, however, two 
pairs of air sacs, one in the thorax and the other towards the end 
of the abdomen, which act as floats, and keep the larva suspended 
horizontally. The last abdominal segment is armed on its ventral 
surface with a vertical fin, which bears a row of feathered bristles. 
The pupa floats in an upright position at the surface of water, and 
has a pair of trumpets on its thorax, not unlike those of the culicine 
pupa. The end of the abdomen is armed with a pair of broad fins, 
by which the larva propels itself. 

Annandale has recently described the larva, pupa, and imago (male) 
of a small gnat, Ramcia inepta, from Peridenyia (4,300 feet), Ce3don. 
Although the fly has a short proboscis, it has a striking culcinae affinity in 
that its veins are partly covered with true scales. The larva, which was 
found in a swamp, is said to resemble somewhat that of the culicid genus 
Stegomyia ; it has a broad triangular head, long jaw-like antennae, and 
distinct thoracic segmentation ; floats and fins are entirely wanting. 

Annandale considers that Ramcia inepta is more closely related to 
the Corethrinae than the Culicinae, but that it links the two groups 
together. 

SUBFAMILY CULICINAE 

Long slender Nematocera, clothed with characteristic scales. Eyes 
kidney-shaped and dichoptic ; ocelli absent. Antenna long, with fourteen 
segments in the female, and fifteen in the male, always pilose in the 
former and plumose in the latter. Palpi four-jointed, either long or 
short in both sexes, or short in one and long in the other ; if short they 
are nearly always straight. Proboscis long and in the female armed 
for piercing, for the majority of mosquitoes are true blood-sucking 
insects; in the male it is simple, and is never used for piercing. 
Scutellutn may be simple, consisting of one lobe, or it may be trilobed, 
and furnished with scales or hairs ; metanotum as a rule well developed, 
and often covered with scales and hairs. Abdomen long aud slender, 
consisting of nine segments, and for the most part covered with 
scales and hairs, especially in the male. Female genitalia consisting 
of two spatulate lateral lobes, covered with scales or hairs. Male 
genitalia composed of two claspers, each with a large basal lobe, and 
a variously shaped terminal knee-like joint ; at the apex of the basal 
segment there is often a well developed spur or spine, which may 
sometimes be bifid. On the ventral surface of the claspers there is often 



SUBFAMILY CULICINAE 



193 



a lohed structure, consisting of one or more spined tubercles, or a long 
acutely hooked process at the apex of the basal lobe. Arising from the 
base of the claspers are the harpes, which are of very varied structure, 
but usually consist of a long blade-like piece of chitin. There is also 
a pair of smaller claspers, usually formed of stout, recurved hooks 
which lie above the harpes. In some species there are processes 
on the ventral margin armed with strong teeth, which are spoken 
of as the unci. Veins of the wings clothed with scales of various 
kinds, the membrane between them being hairy ; light or dark scales are 
often present in patches, thus forming the characteristic light or dark 
spots seen on the wing of Anopheles. The fringe is bordered with scales 
of various kinds. The venation is characterisitc and as follows : — The 
costal vein borders the entire wing, and the subcostal joins it nearer the 
apex than the base; the first longitudinal curves outwards, and on 
turning slightly downwards, ends just above the tip of the wing ; the 
second longitudinal vein is forked, the forks ending at the apex of the 
wing, and enclosing the first submarginal cell; the third longitudinal 
vein is simple and straight, and is united to the veins above and below it 
by the supernumerary* and mid-cross veins (Theobald) ; the third vein 
ends just below the tip of the wing. The fourth vein is forked, the forks 
enclosing the second posterior cell. The fifth vein gives off an anterior 
branch, halfway down its course, and the forks thus formed enclose the 
fourth posterior cell ; the anterior branch is joined to the fourth vein by 
the posterior cross-vein. The sixth vein is simple and somewhat curved. 
When at rest the wings are folded over the abdomen. The legs are long 
and slender, the hind metatarsus is usually long ; the claws are equal and 
small in the female, and may or may not be serrated ; in the male those of 
the fore and mid legs are unequal and serrated, but rarely with more than 
two serrations ; the hind claws are always equal. 

The subfamily Cuhcinae at the present time contains some 1,200 
species, and this number is being added to almost every month. A large 
proportion of the females are blood-suckers, but many never bite, and 
like the males, subsist on plant and similar juices. 

It has already been pointed out that the elaborate classification of 
Theobald has for its basis the structure and arrangement of the scales, 
which clothe the bodies and wings of mosquitoes, so that before taking 

* The supernumerary cross-vein is considered by some dipterologists to be the basal section 
of the third long vein, and not a true cross-vein ; the mid cross-vein is also spoken of as the 
anterior cross-vein (see page 80). 

25 



194 



MEDICAL ENTOMOLOGY 



up the consideration of the genera and species it will be convenient to 

describe some of the common types of scales met with. 
Mosquito Scales . ^ , , ■ j i_ i l j 

(Plate XXXV) scale can be recognized by its ribbed appear- 

ance, the ribs simulating the veins of the wing of an 
insect in miniature. It is nearly always attached by a delicate stalk, 
which is often bifid. Its free end may either be flat with minute serrations, 
or convex with projecting sides ; or sloping gently to a blunt point. 
On the head of a mosquito there are, as a rule, three types of scales to be 
seen. 1. Upright curved scales. 2. Upright forked scales. 3. Broad 
flat scales which are closely applied to the surface. All the three types 
of scales are found on the vertex, and they exhibit great variation in 
colour. 

On the thorax there are commonly four types of scales in addition to 
hairs. 1. Upright curved scales, found all over the thorax and scu- 
tellum. 2. Spindle-shaped recumbent scales, varying in size, and scat- 
tered irregularly over the surface. 3. Flat scales similar to those on the 
head, and found chiefly on the scutellum and just below the roots of the 
wings. 4. Long narrow twisted scales, well marked in the mosquitoes 
of the Mucidus group. 

The scales on the abdomen are best seen in the culicine mosquitoes, 
in which they form a dense covering, and are broad and flat ; most of 
the anophelines have none of these scales, but a few are seen in some 
species, either forming tufts at the sides of the segments, or scattered 
irregularly at the lower end of the abdomen and on the external geni- 
talia. 

The veins of the wing are clothed with a double row of somewhat 
broadly expanded flat scales, and in addition there are often lateral ones 
of varying shape, some long and straight, others curved. In some 
mosquitoes the scales on the wings are more or less ovate, the apical 
border being convex. The wing fringe has two types of scales, one 
short, the other longer ; there are also small border scales, which are flat 
and narrow. 

The legs are always covered with flat scales and hairs, and in some 
species they are greatly exaggerated, and project from the surface. 

The worker will find that any species of Culex, Stegomyia, or Anoph- 
eles will provide almost all the varieties of scales which are likely to be 
met with. 

The eggs of mosquitoes are laid on water, or on any vegetable matter 
lying on its surface ; they may either be deposited singly or in a mass, 
adhering closely together. Most species of the genus Culex, while 



PLATE XXXIV 



Figure 1. 
Figure 2. 
Figure 3. 



Figure 4. 

Figure 5. 

Figure 6. 

Figure 7. 

Figure 8. 

Figure 9. 
Figure. 10 



Larva of Anopheles rossii. x 30. 

Egg of Anopheles sfephensi. x 100. 

Alimentary tract of larva of Cnlex concolor. oes. 

oesophagus, cc, coeca. m.g., mid gut, mp.t., Malpi 

ghian tube, h.g., hind-gut. 

Mental plate of larva of Anopheles rossii. 

Egg of Cnlex fafigans. x 120 about. 

Pupa of Anopheles rossii. x 15. 

Egg of Stegoinyia sugens. X 100. 

Egg of Anopheles fuliginosiis. x 100. 

Egg raft of Cnlex fatigans. X 22. 

Egg of Anopheles cnlicifacies. x 100. 



EGGS OF MOSQUITOES 



195 



depositing the eggs collect them together into a regularly arranged heap 

the so-called egg raft. The female in doing so crosses 

her hind legs arranging each egg as it is passed out. ^^^^^ stages. The 

The egg mass of Culex fatigaiis (Plate XXXIV, fig. 9) *^^^and''xx*xv)'''""^ 

is a typical example of this kind of egg raft ; it is 

boat-shaped and consists of from 200 to 400 eggs. 

The egg (Plate XXXIV, fig. 5) is an elongated ovoid, broadly rounded 
off at the end which lies on the surface film of the water, and which has 
attached to it a delicate globular process, the micropilar apparatus. 
The larva escapes from the broad end, and is thus able to dive 
straight into the water. When first laid the eggs are white, but they 
soon become dark grey. The individual eggs can be readily separated, 
and the whole mass breaks up when the larvae hatch out. 

Many culicines lay their eggs singly, depositing them irregularly 
on the surface of the water, or at its margin. The eggs of these species 
show great structural variation. Some are long and pointed, as those 
of Mansonia and PanopUtes ; in Megarhiniis they are club-shaped, while 
in others they are either spindle-shaped or oval. The eggs of Stegoinyia 
(Plate XXXIV, fig. 7) are surrounded by a frill containing air, and in 
Janthinosoma they are covered with minute spines. 

The eggs of Anopheles (Plate XXXIV, figs. 2, 8 and 10), which are 
also laid separately, are characteristic, being as a general rule boat- 
shaped ; the upper surface is flattened in the transverse diameter, and 
is surrounded by a delicate striated rim or frill. One end of the egg 
is usually broader than the other. Attached to the sides of the egg 
are the floats, which are small ribbed structures containing air ; they 
are present on the majority of ahopheline eggs, though there are some 
remarkable exceptions. Stephens and Christophers have drawn atten- 
tion to the variation in the shape and position of the floats, and in 
the width and extent of the frill on the upper surface. They have 
thus been able to distinguish the eggs of most of the Indian anophe- 
lines. 

When examining the egg of an Anopheles it is important to note 
the character of the frill, whether it is broad or narrow, and whether 
the floats encroach on it. The size and position of the floats should 
also be noted, as well as any other special markings on the surface of 
the egg. 

The body of the culicid larva shows a greater resemblance to the 
adult than is usually the case in the Diptera, being divided into head, 
thorax and abdomen. In their general structure the larvae of the 



196 



MEDICAL ENTOMOLOGY 



Culicinae conform to a common type, of which, however, there are 
characteristic modifications in the different genera. Dyar and Knab have 
used the characters of the larvae as a basis for the 

External structure classification of the Culicinae, and though there is at 
of the larva ' ° 

present no general agreement regarding the value of 

such larval characters, it is often a matter of practical importance 
to be able to recognize species in their larval stage. Even the most 
minute details of the external anatomy are, therefore, worthy of attention. 

As it is in the anopheline mosquitoes that differentiation is the most 
important, Anopheles rossii will be taken as a type, the special char- 
acters which are of use in separating species in this genus being empha- 
sized. The modifications found in the Culicina will be referred to 
subsequently. 

The head of the larva of A. rossii is roughly spherical, slightly flat- 
tened in the dorso-ventral diameter, and narrowed in its anterior third, 

from the point of the insertion of the antennae. The 
appendages posterior border is slightly constricted, and is encircled 

by a collar-like rim of pigmented chitin, continuous 
except at the middle line dorsally, where there is a slight interval. 
From this point a V-shaped suture passes forwards, the two arms 
diverging to extend to the inner side of the base of the antenna. In the 
angle between the two limbs there are several symmetrically arranged 
patches of dark brown pigment, forming a pattern which, although 
subject to slight variation, is characteristic of the species. The dorsal 
surface slopes rather sharply to the distal border of the head, where it 
terminates in a slightly thickened transverse bar, termed by some writers 
the clypeus, by others the labrum. Arising from, or slightly behind, 
this border there are two pairs of hairs, termed the clypeal or frontal 
hairs. The external pair of these project forward on each side over the 
feeding brushes, and are on this account not always easy to distinguish. 
The internal hair is set nearer the edge, and projects in the interval 
between the feeding brushes. In rossii both these hairs are simple 
and unbranched*, but in other species they may be forked or branched 
forming a complete cockade, thus affording a valuable distinguishing 
feature. About the middle of the head there is on the dorsal surface an 
arched transverse row of six large feathered hairs, all of which project 
upwards and forwards, reaching as far as the distal border of the head. 
Behind these, and on each side of the pigment spots between the arms of 



* A hair is said to be branched when the branches He in more than one plane, and 
feathered when all are in one plane (Nuttall and Shipley). 



ANOPHELES ROSSII : LARVA 



197 



the V-shaped suture, there is another row of four smaller hairs, and 
further back a pair of small simple hairs. 

The antennae arise from the sides of the head a little in front of its 
middle point. They are generally described as two-jointed, the basal 
joint being fused with the head wall. The projecting portion in rossii 
is a simple cylindrical and tapering organ, usually directed forwards, 
but capable of movement in a lateral direction. Its surface is sparsely 
covered with short recumbent hairs, and at the distal end there are two 
short spines, projecting from a papilla which is probably sensory in 
function. In many species there is a plume of hairs on one side of the 
antenna, inserted at varying distances from the base, and known as the 
hasal tuft. This is represented in rossii by a single short hair, easily 
overlooked if the side on which it lies happens to be away from the 
observer. The terminal portion at the base of the papilla may also bear 
hairs, those found in this situation being usually shorter and stouter than 
the proximal ones. The papilla itself may be lengthened — though not in 
Anopheles — to form a distal joint. 

The eyes vary a good deal according to the age of the larva, as 
bpth the primitive larval eye and the early stages of the developing eye 
of the adult are present. The former is seen as a round or oval patch of 
pigment situated behind the insertion of the antenna, while the com- 
pound eye appears as a collection of isolated pigment spots slightly 
dorsal to this ; they often show a crescentic outline. 

The ventral surface of the head is more irregular than the dorsal, 
a considerable part of the anterior area being occupied by the mouth 
parts. There is a median longitudinal suture extending forwards from 
the collar, and a lateral suture some distance on each side of this. 

The mouth is adapted for the ingestion of minute particles, and is 
provided with an apparatus for setting up a current in the water to 
attract them, the larva remaining stationary or at the most turning round 
in a circle as it feeds ; the particles are entangled in a sieve-like arrange- 
ment of hairs, the water being discarded and the food swallowed. The 
structures which form the mouth are the feeding brushes and certain 
accessory bunches of hairs, the mandibles and first maxillae, and the 
mental plate, with which is connected the hypopharynx. 

The feeding brushes are dense masses of long fine hairs, set one on 
each side of the distal end of the head. Each is attached to a thickened 
ridge of chitin at the side of the ventral margin, and is provided with 
two muscles, by means of which it can be rotated inwards, and at the 
same time retracted within the oral cavity. In the resting position the 



198 



MEDICAL ENTOMOLOGY 



bunches of hairs are spread out and project well in front of the 
clypeus ; they do not present any special modifications of taxonomic 
value. In predaceous larvae the hairs are much fewer in number, and 
are much stouter, and may be serrated ; such larvae use their feeding 
brushes in seizing their prey. (James.) 

Between the feeding brushes, in the middle of the ventral margin, 
there is a bunch of seven stouter hairs, directed forwards like a plume. 
These move with the feeding brushes, as they arise from the same mem- 
brane as that in which the apodemes of the latter are developed. 

The mandibles (Plate XXXV, fig. 1) are stout, somewhat quadrilateral 

appendages, consisting of a single joint, the two forming the lateral 

boundaries of the mouth aperture. The anterior and 
The Mandibles and , . j -^i . r j i i i 

Maxillae mner angle is armed with a set oi dark brown chitinous 

teeth, apparently of little use in most anopheline 

larvae, which are surface feeders. On the anterior and external angle 

there is a group of four strong curved hairs, bent inwards over the teeth ; 

these are used in cleaning the brushes. On the internal border there 

is a fringe of fine hairs, those of the two sides meeting when the 

mandibles are folded inwards. In the normal resting position the teeth 

of the mandibles lie near one another and immediately in front of 

the mental plate. They can be rotated outwards on their posterior and 

external angles through an angle of 90° or so. 

The maxillae (Plate XXXV, fig. 4) are partly covered by the 
mandibles, and are neither easy to see when in sitil nor to dissect out. 
Each consists of a flattened and irregular chitinous plate, covered 
with fine stiff hairs which are mainly directed towards the anterior and 
internal angle, and are used, like those of the mandibles, in cleaning the 
feeding brushes. On the outer side of the maxilla there is a small 
spindle-shaped palp, the distal end of which is surmounted by three small 
stout spines, connected together by a membrane. The palp lies internal 
to the antenna, and is the most conspicuous part of the appendage. 
Neither mandibles nor maxillae afford useful distinguishing characters. 
The maxillary palp is small in most species of Culex and Stegomyia. 

The mental plate (Plate XXXIV, fig. 4) lies in the middle line, at the 
posterior end of the mouth area, and between the two mandibles. It is 
small, triangular, and heavily pigmented, having its apex pointed and 
directed forwards, and its sides divided into a number of coarse serrations. 
This structure probably represents the rudiments of two fused maxillae, 
and is indeed termed the labial plate by some writers ; others have pointed 
out its correspondence with the mentum of other larvae. In reality the 



PLATE XXXV 



Figure 


1. 


Figure 




Figure 


3. 


Figure 


4. 


Figure 


5. 


Figure 


6. 


Figure 


7. 


Figure 


8. 


Figure 


9. 


Figure 


10. 


Figure 


11. 


Figure 


12. 


Figure 


13. 


Figure 


14. 


Figure 


15. 


Figure 


16. 


Figure 


17. 



Mandible of larva of Anopheles rossii. 

Upright forked scale, after Theobald. 

Upright forked scale, after Theobald. 

Maxilla of larva of Anopheles rossii. 

Twisted upright scale, after Theobald. 

Broad wing scale from Paiioplites, after Theobald. 

Inflated parti-coloured scale, after Theobald. 

Broad wing scale from Aedeoiiiyia, after Theobald. 

Small spindle-shaped scale, after Theobald. 

Curved hair-like scale, after Theobald, 

Flat spindle-shaped scale, after Theobald. 

Narrow curved scale, after Theobald. 

Flat scale from abdomen, after Theobald. 

Spine from syphon tube of Cnlex larva. 

Syphon tube and 8th and 9th abdominal segments of 

larva of Stegoinyia siigens. 

Syphon tube and 8th and 9th abdominal segments of 

larva of Cnlex fatigans. 

Palmate hairs of larva of Anopheles rossii. 




19S 



t 

i 



ANOPHELES ROSSII : LARVA 



199 



plate consists of two parts, one lying dorsal to the other, so that they 
appear as one when seen from above. The upper of these would corre- 
spond to the mentum, which has become displaced backwards behind the 
submentum. The salivary duct traverses the median area and opens at 
its tip. 

The larva of Anopheles is a surface feeder, and therefore assumes an 
attitude parallel with the surface, retaining its position by means of the 
palmate hairs on the abdomen. The head can be rotated through 
an angle of 180°, so that the ventral surface becomes dorsal. The feeding 
brushes are moved rapidly inwards, and at the same time retracted, a 
succession of these movements setting up a current which carries any 
solid particles within reach towards the mouth. They are then secured 
and swallowed, while the water is allowed to escape. From time to time 
the stout hairs on the mandibles, and the shorter hairs on the maxillae, 
are used to remove the particles from the brushes, and to rearrange them. 

The thorax, like that of the adult, does not show any clear divi- 
sions into segments. It is rounded in shape, and bears on its dorsal 

and lateral surfaces three rows of feathered hairs. The 

. , . . J 1 <■ Thorax and abdomen 

most anterior or these is situated at the front margin, 

and consists of six hairs which overhang the head. The second row 
lies a little behind the first, while the third, which consists of larger 
hairs than the preceding, is placed at the junction of the middle with 
the anterior third. The thorax is relatively much larger in adult than 
in young larvae, and in some species of Anopheles it may be furnished with 
palmate hairs, like those on the abdomen, to be described presently. 

The abdomen consists of nine segments, diminishing gradually in 
size from before backwards. The first seven resemble one another, 
and are broadest in the transverse diameter ; the eighth bears the 
respiratory opening, and the ninth the anus, with certain special struct- 
ures. Each of the first three segments is furnished with a pair of long 
feathered hairs, directed forwards and outwards, and inserted on slightly 
raised areas at the lateral borders. The remaining segments are armed 
with simple hairs, and there are on each segment several smaller ones, as 
well as on the raised lateral areas. None of the structures afford 
reliable distinguishing characters. 

The palmate hairs (Plate XXXV, fig. 17) are minute but elaborate 
structures, by means of which the larva is enabled to cling to the 
surface film. They are situated on the lateral part paimate ha' 
of the dorsal surface of the abdominal segments, and 
are peculiar to the Anophelina. The number varies in different species ; 



200 



MEDICAL ENTOMOLOGY 



they may be present on all the abdominal segments, as well as on 
the thorax, or they may be confined to the more posterior segments. 
Each palmate hair consists of a number of delicate leaflets arising from 
a common stalk, and arranged in a radiating manner like the ribs of a 
half-opened umbrella. The basal portion of each leaflet is broad, and 
often appears concave, while the distal portion is usually narrowed and 
pointed. The edges of the leaflets may be notched in a characteristic 
manner. In rossii there is a small notch on one border. The number — 
nineteen in this species — and shape of the leaflet, are of specific 
importance. 

The eighth segment bears the respiratory openings or stigmata, the 

terminations of the large lateral tracheae which traverse the whole 

„ . ^ . length of the larva. These lie in the anterior part 

Respiratory opening ^ . j w i ^ i 

oi an irregularly quadrilateral area on the dorsal 

surface. This area is raised a little above the level of the preceding 
segment, and is supported by a chitinous arch, the lateral arms of 
which are provided with a series of spine-like teeth, corresponding to the 
' comb ' of the larva of Ciilex. The anterior and lateral margins of 
the space in which the stigmata lie can be turned inwards so as to 
partly arch over the area, or again retracted when the larva is breathing. 
The raised portion is pushed through the surface film during respiration, 
so that the tracheae are in free communication with the air through the 
openings of the stigmata. When the larva sinks to the bottom, the 
openings are closed by the arching over of the sides of the area. 

The ninth segment is narrower and rounder than the rest, and is a 
little elongated. Its dorsal border is furnished with two pairs of long 
feathered hairs, which are directed backwards as a tail. The ventral sur- 
face bears two rows of feathered hairs, arising in the middle line from an 
elongated and raised area of thicker chitin. The two rows are set very close 
together, so that when examined in side view they appear as one, and 
hang down at a right angle to the long axis of the body as a sort of fin ; 
each hair is articulated into a little round pit in the chitinized area. 
Between the dorsal and ventral sets of hairs there are four similar and 
symmetrically arranged papillae. These are delicate transparent leaf-like 
structures, possessing a considerable amount of retractility. They are 
small in Anopheles, as it is a surface feeder, but become of considerable 
size in those larvae, such as some species of Stegomyia, which feed 
almost exclusively at the bottom of the water. These organs are 
invaginations of the body wall, and, as they contain blood, function as 
tracheal gills. 



CULEX AND STEGOMYIA: LARVAE 



201 



In all culicid larvae other than Anopheles the openings of the tracheae 
lies at the end of a tube of chitin of varying length, known as the syphon. 
This has the form of a cylinder, arising from the dorsal 
surface of the eighth segment, and usually narrowing (pia^e''xxxv'''figs 
a little towards the distal end. The apex is closed by ^5 iq) 
a series of finger-like flaps of chitin, which can be opened 
when the larva ascends to the surface to breathe. At the base there is 
a thickened ring by which the syphon is attached to the eighth segment, 
and it is at this point that the tube, as a rule, attains its greatest breadth. 

Christophers regards the shape of the syphon tube as a point of 
considerable taxonomic value, and has used as a taxonomic character the 
'syphonic index,' obtained by dividing the length of the tube by its 
greatest breadth. The tube may be short and stout, or it may be of 
extraordinary length and very narrow. It may be furnished with several 
branched or simple hairs. On each side there is a row of peculiar spines, 
the number of which is important ; these may be arranged in a regular 
row, or the row may be interrupted. At the base of the syphon, on the 
dorsal surface of the eighth segment, there is a row of spines represent- 
ing the comb which surrounds the respiratory opening in Anopheles. 

Apart from the presence of the syphon tube, there are many minor 
differences between the larvae of different genera. The head, for 
instance, is larger in Ciilex than in Anopheles, while in Stegomyia 
both head and thorax are relatively small. The antennae in Stegomyia 
are small and degraded, and have no small recumbent hairs, while the 
papilla is often well developed. In the genus Culex the antenna 
may show great variation. Striking deviations from the type are 
to be found in cannibal larvae, such as that of Ciilex concolor. In 
this species the syphon tube is short, and the larvae, therefore, either 
float almost horizontally on the surface or with their heads a little 
below it ; in this position they remain stationary, waiting for their 
prey. The feeding brushes, as already noted, are transformed into 
clasping organs, and the clypeus is concave instead of straight. 

The differences between the larvae of species even in well estab- 
lished genera are so great that they cannot be profitably discussed 
here. The character of each species with which the worker is con- 
cerned should be determined by an actual examination of the living 
larva between a slide and cover glass, and the specimens subsequently 
bred out and identified, the larval skin being retained for reference. 
The points which are of special importance are the presence or 
absence of hairs or spines on the antennae, the shape and number 
26 



202 



MEDICAL ENTOMOLOGY 



of the teeth on the mental plate, the syphonic index, the number of spines 
on the syphon tube, and in the comb at its base. It is particularly 
important to note whether the larva is carnivorous or not ; if it is 
it must be bred with a known species with which it cannot be mis- 
taken. The worker should be careful to compare only larvae of 
approximately the same size and age, as the later stages differ from 
the early one in some particulars. The hairs are generally more 
numerous and more branched in the full grown larva than in young 
specimens. 

The alimentary tract of the larva (Plate XXXIV, fig. 3) is a simple 
one, and when dissected out is only a little longer than the body. 



seen through the integument in living larvae. The oesophagus is a 
short and narrow tube passing through the neck, with a large 
amount of muscular tissue in its walls, mainly arranged in circular 
fibres. In the thorax it becomes continuous with the first part of the 
mesenteron. The junction between the two is effected in very much the 
same way as in the adult Philaeinatomyia already described, the end of 
the oesophagus being invaginated into the commencement of the mesent- 
eron so as to produce a valve. The space between the two walls of 
the invaginated portion is a considerable one, and is probabl)', according 
to Imms, a blood sinus. Immediately below the valve there are eight 
coeca ; these are short but broad sacs, constricted in the middle, the 
set being arranged in a regular row around the entrance to the mid-gut. 
The cells of the coeca secrete a granular material which is excreted 
into the lumen ; they stain very deeply with haematoxylin. The 
mid-gut extends as far as the eighth segment, and is the same shape 
as the cavity in which it lies, and is not convoluted. Its wall is 
lined with a secreting epithelium similar to that in the adult insect. 
There is in the larva, however, a well developed peritrophic mem- 
brane. There are five rather short and stout Malpighian tubes, both 
in the larva of Ciilex and Anopheles. The hind-gut consists of a 
short and narrow ileum, well supplied with circular muscle fibres, 
and a wider pear-shaped portion, the colon, with which is included 
the rectum. There are no rectal papillae, these being probably re- 
presented by the external tracheal gills. The wall of the hind-gut has 
a well marked chitinous intima. 

Many mosquitoes are naturally infected with flagellates of the genera 



Internal structure 
of the larva 



The mouth leads into an oval or roughly quadrilateral 
pharynx, actuated by a complex musculature, which 
is situated in the middle of the head, and can be 



ANOPHELES ROSSII : PUPA 



203 



Herpetomonas and Crithidia, and the hind-guts of their larvae are 
the chief situations in which the parasites undergo their early develop- 
ment ; in an infected larva they may be seen in large numbers massed 
together in the form of a palisade along the epithelial lining. 

Mosquito larvae moult three times, completely shedding their skins 
before they are ready to pupate ; the organs of the imago commence 
to form during the last larval stage. The buba emerges 
through a shf on the dorsal surface. Its kppearance ".'xxir,'™" 
is very characteristic ; it consists of a rounded body 
composed of the head and thorax, and an elongated abdomen flattened 
dorso-ventrally, and held underneath the body. The bulbous por- 
tion is enclosed in a delicate cuticle, through v\'hich the appendages 
of the developing imago can be readily made out. The antennae 
appear as lateral ridges arising above and in front of the com- 
pound eyes ; they pass backwards over the legs to end in front 
of the wings. Arising from the dorsum of the thorax there 
are two stout tubes, the respiratory trumpets. These are con- 
stricted at their attached ends, but expanded distally, opening to 
the exterior by a V-shaped slit, which is directed inwards and 
guarded by a number of delicate hairs ; the narrow ends of the 
trumpets are continuous with the lateral tracheae. Christophers has 
pointed out that the shape of the slit and the manner in which the 
trumpets project from the thorax are of generic significance. In 
Anopheles the trumpets are short and arise from the middle of the dorsum 
of the thorax, and have truncated ends ; in Culex they arise from the 
posterior part of the thorax, are long and narrow, and the opening is 
somewhat oblique, while in Stegomyia the tubes are short and broad, 
and the openings triangular in shape. 

The abdomen of the pupa consists of nine segments, the first of which 
is not clearly seen; its dorsal plate appears as a wedge between the 
base of the wings. The second segment and the remaining six are 
flattened dorso-ventrally ; each dorsal plate is well developed, covering 
almost the entire segment, and its sides are thickened and furnished 
with posteriorly directed hairs, The eighth, segment is armed with two 
large chitinous flaps, the fins, each being supported by a stiff bar which 
runs horizontally across to end in a hair at the free margin. The 
ninth segment has a pair of blunt processes lying between and in front 
of the fins ; in the male they form a broad heart-shaped protuberance; 
in the female they are smaller, andT thus afford a means of distinguishing 
the sex of- tl>e future imago. . .. .. ..... 



204 



MEDICAL ENTOMOLOGY 



The pupa of Anopheles is elongated antero-posteriorly, and as a rule 
hangs in the water in a much less vertical position than that of Culex, 
which is not so much elongated. 

As the pupa increases in age additional hairs are developed and 
its body becomes darker in colour. Just before the fly emerges it comes 
to rest, and extends its abdomen ; the dorsum of the thorax now splits, 
and the adult insect slowly extricates itself. As a rule the pupal stage 
lasts from three to four days, according to the temperature ; it may be 
as short as forty-eight hours and as long as ten days. 

James and Liston's Key to the identification of the known larvae of 

Indian Anopheles. 

1. Antennae with a large branched hair 

A. With simple unbranched frontal hairs .... lindesayi- 

B. With branched frontal hairs. 
1. 



Median frontal hairs unbranched. The branches of 
the external frontal hairs arise from the main stem 
and from other branches ...... 

2. Median frontal hair unbranched. The branches of the 
external frontal hairs arise from the main stem only. 

Antennae without a large branched hair. 

A. With fully developed palmate hairs on the thorax. 
(a) With simple unbranched frontal hairs. 

1. The filaments of the palmate hair leaflets rather long. . 

2. Palmate hairs very large on thorax. Filaments shorter. 

Characteristic head pattern . . . . . 

3. Basal hairs characteristic 

(6) With branched frontal hairs. 

1. Two branched posterior hairs in addition to the frontal 

hairs. Palmate hairs large. Filament short 

2. No posterior hair 

B. Without fully developed palmate hairs on the thorax. 
(a) With simple unbranched frontal hairs. 

1. Characteristic head pattern. Filaments of leaflets long. 

2. No head pattern. Filaments shorter .... 

3. Filaments very short and blunt ..... 

4. Filaments short, sharp-pointed ..... 
5- Two long unbranched posterior hairs. Palmate hairs 

only on the last few abdominal segments 
(6) With branched frontal hairs. 

1. Frontal hairs much branched ..... 

2- Frontal hairs only slightly branched or frayed 

3- External frontal hairs unbranched, median forked 



barbirostris. 



sinensis 



culicifacies. 

listoni. 
culiciformis. 



jeyporiensis. 
maculipalpis. 



rossii. 
Stephens!, 
theobaldi. 
maculatus. 

turkhudi. 

fuliginosus. 

pulcherrimus. 

aitkeni. 



Edward's Key to the known larvae of African Anopheles. 

1. Shaft of antenna with hair-tuft; no plumose hairs in 

middle of thorax overlapping occiput .... muriti^nus. 



CULICINAE: CLASSIFICATION 



205 



Shaft of antenna without hair-tuft ; plumose hairs present 

in middle of thorax in front ......... 2 

2. Rudimentary palmate hairs on thorax .... ... 3 

Palmate hairs of thorax altogether wanting ... . . 6 

3. External anterior frontal hair much branched, forming a 

pronounced tuft squamosus ; 

pharoensis. 

External anterior frontal hair simple or slightly branched .... 4 

4. Posterior and internal anterior frontal hairs simple . . funestus. 
Posterior and internal anterior frontal hairs branched .... 5 

5. Dark brown ; filaments of palmate hairs longer . . . natalensis. 
Light brown ; filaments of palmate hairs shorter . . ardensis. 

6. Median thoracic hairs overlapping occiput rudimentary . maculipennis 
Median thoracic hairs overlapping occiput well developed .... 7 

7. Internal anterior frontal hair branched ....... 8 

Internal anterior frontal hair simple ........ 9 

8. Palmate hair on second abdominal segment fully develop- 

ed, the leaflets with a distinct shoulder ; filaments of all 
palmate hairs about one-third as long as the whole leaflet, costalis. 
Leaflets of palmate hair on second abdominal segment 
without shoulder ; filaments of all other palmate hairs 
under one-quarter as long as the whole leaflet . . jacobi. 

9. Hair at tip of antennae between the two spines split into 

two cinereus. 

Hair at tip of antennae split into three . . . . . .10 

10. Palmate hair on second abdominal segment well developed, pretoriensis. 
Palmate hair on second abdominal segment rudimentary . ruf ipes. 

As has already been pointed out, Theobald places the mosquitoes 
in a separate family the Culicidae, which he divides it into ten subfamilies. 
The classification adopted by him and his followers 
has not, however, met with universal approval. Willis- ^j^^ Culicinae 
ton, one of the foremost systematic dipterologists, 
points out that nearly all the present-day culicidologists appear to have 
a limited knowledge of related Diptera, and as a result have disregarded 
broad zoological relationships and have erected subfamilies and genera 
on characters of minor value. He instances the subfamily Hep- 
taphlebomyinae, which is erected on the single character of the 
presence of scales on the seventh longitudinal vien. He considers that 
scale characters are artificial, and that although they may be useful 
in separating the higher groups, they are of little use in splitting up 
genera ; it is here that they are apt to be overrated. Williston's paper 
on the Classification of the Culicidae, and his remarks on the same 
subject in his ^^olume on North American Diptera, should be read by 
all interested in the subject. 

. .The following table, which gives the chief characters of the Culicidae, 
is taken from Volume IV of the Culicidae of the World. 



206 



MEDICAL ENTOMOLOGY 



Theobald's Table of the Subfamilies of the Culicidae. 

A. Scutellum simple, never trilobed. Proboscis straight ; 

palpi long in male and female Anophelinae. 
AA. Scutellum trilobed. 

a. Proboscis strongly recurved ; first submarginal cell very- 
small , . Megarhininae. 

aa. Proboscis straight ; metanotum nude. 

1,. Wings with six long-scaled veins ........ 2 

Wings with seven long-scaled veins ..... Heptaphle- 

bomyinae. 

2- Antennae with second joint normal in length 3 

Second segment of antennae very long .... Deinoceratinae. 

3. First submarginal cell as long or longer than second pos- 

terior cell 4 

First submarginal cell very small, smaller than second 

posterior cell Uranotaeninae. 

4. Palpi of female shorter than proboscis, of the male longer- Culicinae. 
Palpi short in male and female ...... Aedinae. 

aaa. Proboscis straight ; metanotum with scales or chaetae , 

5. Palpi long in male short in female Trichoprosopn- 

inae. 

Palpi short in male and female Dendromyinae. 

aaaa, Proboscis elbowed Limatinae. 

Alcock suggests a simpler grouping of the Culicinae (sensu late), 
which he divides into four sections as follows : — 

Section I. Megalorhinina (Megarhininae, Theobald). Mosquitoes in 
which the proboscis is very long and curved downwards, the apical 
part being much thinner than the basal. Palpi of the female either 
short or long. Wings narrow and somewhat elongated, the first ' fork 
cell ' shorter than the second. Large, usually blue or green mosquitoes, 
non-biting, and with predaceous larvae. 

Section 2. Culicina (Culicinae, Heptaphlebomyinae, Dinoceratinae, 
Aedinae and Uranotaeninae, Theobald). Mosquitoes in which the pro- 
boscis is of the usual type but not recurved ; head clothed with different 
types of scales ; palpi in the male long or short, many gradations existing 
between the two. Thorax round with a trilobed scutellum thickly 
covered with scales ; metanotum without hairs or bristles. Wings, 
though rarely spotted, may be speckled or mottled. 

Section 3. Metanotrichinia (Trichoprosopinae, Dendromyinae and 
Limatinae, Theobald)- Mosquitoes in which the proboscis is of the 
usual type ; the head, scutellum, and sometimes the thorax, are clothed 
with flat scales; palpi may be short in both sexes, or short in the 
female alone. Metanotum with a few bristles. . ; - 

Section 4. _ Anophelina (Anophelinae, Theobald). Mosquitoes- in 
which the proboscis is of the usual type^ the head-is clothed .with upright 



THE MEGALORHININA 



207 



forked scales, and never with flat scales ; palpi as long as the proboscis 
in both sexes. Dorsal surface of thorax seldom denselj' clothed with 
scales. Scutellum simple, not lobed. Abdomen clothed with hairs or 
scales, the latter, if present, usually confined to the last segments, and 
then often inconspicuous. Wings as a rule spotted. 

THE MEGALORHININA 

This group of mosquitoes, according to Theobald, contains three genera 
Megarhinus, Robineau-Desvoidy, Ankylorhynchus, Lutz, and Toxorhyn- 
chites, Theobald ; some of them are the most brilliantly coloured of all 
the mosquitoes ; many of them have caudal tufts of hair-like scales on 
each side of the abdomen. Their large size, bright colours, and long bent 
proboscides are points which help in recognizing them. In Megarhinus 
and Ankylorhynchus the palpi are long in both sexes ; in the former the 
last palpal segment in the female is rounded off, while in the latter it is 
round and pointed. In Toxorhynchites the palpi of the female are 
short, about one-third the length of the proboscis. 

Theobald recognizes eleven species of Megarhinus, which are confined 
to North and South America and the West Indies ; he states that the 
species described from India and Ceylon probably belong to Toxorhyn- 
chites. Peryassu and Bourroul have figured and described the larvae of 
some of the Brazilian species ; they are all predaceous, and are found in 
water-buts and in holes in trees, where they live entirely on other mos- 
quito larvae. The anal fin is wanting, but the terminal segment has four 
knob-like processes. The thorax is furnished with stout serrated spines 
and the abdomen has dense lateral tufts ; the breathing syphon is rather 
short and ends in a valve with four flaps ; the mandibles are very power- 
ful. The whole larva is often blotched or streaked. The pupa has 
curved breathing trumpets, and two well-developed caudal fins. The 
eggs are elongated, pointed at one end and somewhat blunt at the other. 

There are four species of Ankylorhynchus from South America, one of 
which has no caudal tufts at the end of the abdomen. 

Theobald describes twenty-three species of Toxorhynchites from various 
parts of the world. T. immisericors is a common species in India, and 
breeds in holes in trees, in tanks, water-buts and tubs in which water 
is allowed to collect. The larvae are predaceous, though, in the case 
of some of the species, they do not feed on their own kind ; the eggs 
are laid singly. 



208 



MEDICAL ENTOMOLOGY 



THE CULICINA 



This section contains the well-known culicine mosquitoes, in which 
the scutellum is trilobed. The palps show extreme variations in length, 
some being as long or longer than the proboscis, others much shorter ; 
they are, however, usually long in the male and short in the female, or 
moderately short in both sexes. Dyar and Knab have come to the con- 
clusion that the length of the palps is a character of minor importance, 
and that too much stress should not be laid on it in splitting up the 
group. The character of the scale ornamentation is also very variable. 

The Culicina (sensu lato) comprises the subfamilies Culicinae, Hep- 
taphlebomyinae, Dinoceratinae, Aedinae, and Uranotaeninae of Theobald. 
Many of these groups contain a large number of genera, which cannot 
be described in detail here for want of space. The following table of the 
important genera is taken from Theobald's monograph, to which the 
reader is referred for further details. 

Theobald's table of genera of the subfamily Culicinae (sensu restricto). 
L Eyes and scutellum normal. 

A. Legs ornamented with dense outstanding scales. 

Head clothed with spindle-shaped and broad curved 
scales. 

Hind legs only densely scaled 



All the legs more or less densely scaled. 

Wing scales rather thin .... 

Wing scales large inflated parti-coloured. Body 
and head with very long twisted scales 

B. Legs normal, no irregular scales. 

» Head clothed with flat and upright forked scales only. 
/3 Scutellum with flat scales. 

Small flat scales on the mesonotum before 
scutellum ....... 

Flat scales as lateral patches also . 

No flat scales on mesonotum. 

Male papli long, thin, nude and acuminate. 
Large ....... 

Flat scales over the wing roots ; proboscis 
very short and thick, bent twice ; mid ungues 
of male equal ...... 

Male palpi thin, acuminate or clavate, hairy. 
Small 



Janthinosoma 

(Aedes group). 

Psorophora 

(Aedes group). 

Mucidus 

(Aedes group). 



Quasistegomyia 

(Aedes group). 
Kingia 

(Aedes group). 



Desvoidya 

(Aedes group). 



Brevirhynchus 

(Aedes group). 

Stegomyia 

(Aedes group). 



GENERA OF SUBFAMILY CULICINAE. THEOBALD 209 



Ventral abdominal scale tufts . . , 

Scutellum with narrow-curved scales. 

Palpi of male acuminate ..... 

Palpi of male clavate ..... 

Palpi of male clavate, marginal cell much con- 
tracted posteriorly. Shiny , , , . 

/S/S/3 Scutellum with flat scales at the base of the 
mid-lobe, narrow-curved at the border and a 
few on the lateral lobes. Legs very shiny 

dCl Head clothed with mostly flat scales but also with 
small areas of narrow-curved scales and upright 
forked ones. 

7 Scutellum with all flat scales. 
^ Palpi of female \'ery short. 

Head with a median row of narrow-curved 
scales . 

Plead with narrow-curved scales behind . 

Apex of abdomen very bristly ; male palpi 
two-thirds the length of the proboscis. 
No hair tufts ..... 

Apex of abdomen very bristly ; palpi of 
male smaller ; wing scales straight Imear 
and narrow spatulate .... 

Palpi of female half length of proboscis. 
Head with flat scales e.xcept for some 
spindle-shaped ones around the eyes 

As above, but a row of narrow-curved 
scales bordering eyes .... 

77 Scutellum with flat scales to mid lobe, narrow- 
curved ones to lateral lobes. 

Head with flat scales, narrow-curved ones 
in median area ..... 

Head with all fiat scales except for a 
median basal area ..... 

777 Scutellum with flat scales on each lobe separat- 
ed by narrow-curved ones, an apical border 
of narrow-curved scales .... 



Pseudocarrollia 

(Aedes group). 

Pseudoskusea 

(Aedes group). 
Ludlowia 

(Aedes group). 

Radioculex 

(Aedes group). 



Chaetocruiomyia 

(Aedes group). 



Scutomyia 

(Aedes group). 
Aedimorphus 

(Aedes group). 



Rachisoura 

(Aedes group). 



Mimeteomyla 

(Aedes group). 



Leicesteria 

(Aedes group). 

Duttonia 

(Aedes group). 



Macleaya 

(Aedes group). 

Carrollia 

(.Aedes group). 



Popea 

(Aedes group). 



27 



210 



MEDICAL ENTOMOLOGY 



7777 Scutellum with flat and narrow-curved scales, 

none along apical border .... Howardina 

(Aedes group). 

77777 Scutellum with large spindle-shaped scales . Huleocoeteomyia 



777777 Scutellum with small flat scales on mid-lobe, 

narrow-curved ones on lateral lobes . . Phagomyia 



.\edes group). 

lagomyia 

(Aedes group) . 



Scutellum. with small narrow flat scales 
on mid-lobe, narrow-curved ones over 
back, sides and border ; lateral lobes with 
large narrow-curved scales. Wing scales 
Taeniorhynchus-hke .... Myxosquamus 

(Aedes group) ? 

•olyleptiomyii 

(Aedes group). 



7777777 Scutellum with spindle-shaped scales on mid 

lobe, flat ones on lateral lobes . . . Polyleptiomyia 



77777777 Scutellum with narrovv-cur\ed scales all over. 

B Head with flat scales e.xcept for a median 

triangular narrow-cur\'ed scale area . Pseudohowardinia 

(Aedes group). 

as Flat scales spread around the eyes . . Culiciomyia 

(.\edes group). 

Flat scales loose ; male palpi without 
hair tuft ; shorter than proboscis . . Eumelanomyia 

■? 

Head with only a double row of narrow- 
curved median scales .... Neomacleaya 

(Aedes group). 

BBBB Head with all flat scales except along the nape Danielsia 

Gualteria 

Prothoracic lobes all with thick chaetae ; 

fork cells small Hispidimyia 

8BBBB Head with narrow-curved scales around the 

eyes Lepidotomyia 

(Aedes group). 

BBBBBB Head with narrow-curved scales behind . Onophodromyia 

(.\edes group). 

aua Head clothed with mostly narrow-curved scales and 
upright forked ones, flat only at the sides as in 
Culex. 

Scutellum with flat median and narrow-curved 
lateral scales Protomacleaya 

(Aedes group), 

Scutellum with all flat scales .... Reedomyia 

(.\edes group). 

Scutellum with mi.xed narrow-cur\-ed and small 
flat scales to mid lobe, long, flat and narrow- 
cur\ ed ones to lateral lobes .... Pecomyia 

(Aedes group). 



GENERA OF SUBFAMILY CULICINAE. THEOBALD 211 



Scutellum with all flat scales, but a broad 
apical area to the mid lobe and some scattered 
■ ones on the lateral lobes ■ , , . . Neopecomyia 

:\edes group). 

enoscutus 

(Aedes group). 

ithosomyia 

(Aedes group). 



Mid lobe of scutellum with broad curved scales 

lateral lobes with flat and narrow-curved ones. StenoscutUS 

Scutellum with narrow-curved scales ; first 
posterior cell uniform in breadth . . Bathosomyia 



0/0/0/0/ Head with loose irregular flat scales and narrow- 
curved ones behind. 

Scutellum with flat median scales and narrow- 
curved lateral ones ..... Catageiomyia 

(Aedes group). 

aao/O/a Head with broad flat spindle-shaped scales. Scutellum 
with small flat scales. 

Vein scales of Tacniorhynchns type . . Gilesia 

(Aedes group). 

Antennae densely hairy , ' . . . . Trichorhynchus 

(Aedes group). 

O/aOiaaO/ Head with broad narrow-curved scales ; scutellum 

with flat scales ; male palpi clavate, wings spotted. Pseudotheobaldia 

(Culex group). 

Scutellum with broad spindle-shaped scales . Maillotia 

(Culex group). 

O/O/O/aO/aOi Head and scutellar scales narrow-curved only, 
except at the sides of the head where they are flat. 
S Abdomen clothed with flat scales only. 
I. Legs uniform, femora not enlarged at all. 

Palpi of male clavate. Wings with lanceolate 
scales united into spots ..... Theobaldia 

(Culex group). 

Wing scales scanty ; wing membrane stained . Pardomyia 



Wing scales pear-shaped and spatulate ; fork cells 
short Megaculex 



(Culex group). 

egaculex 

(Culex group). 



Wings with rather thick median scales and short 
broadish lateral ones. Fork-cells small ; scales 
mottled. 

Head with broad narrow-curved scales and 
forked ones. 

Scutellum with narrow-curved scales . . . Grabhamia 

(Aedes group). 

With mostly small flat scales on the scutellum, a 
few narrow-curved ones on posterior border of 
mid lobe Pseudograbhamia 



Head with irregular flat scales dotted all over 
giving a ragged appearance . . . Acartomyia 



(Aedes group). 

artomyia 

Aedes group). 



MEDICAL ENTOMOLOGY 



Posterior cross-vein slopes prominently in basal 
direction, and median vein scales large and 
spatulate. . t t • . . . Aporoculex 

(Culex group). 

Palpi of male acuminate. Wings ornamented 
with various coloured patches. Scales partly 
C/(/eA;-like, partly Tacniorhynchus-\ike . . Lutzia 

(Culex group). 

Wings with dense linear scales ; fork cells short. Culicada 

(Aedes group). 

Wings with broadish lateral vein scales, median 
large and spatulate. Front area of thorax 

silvery-grey scaled Leucomyia 

(Culex group). 

Fork cells short, but vein scales broader than in 
Culex ........ Culicelsa 

(Aedes group). 

Wings with narrow linear or lanceolate scales. 
Fork cells long in the female. Costa not mark- 
edly spinose Culex 

Costa spinose ; male palpi bluntly acuminate. Microculex 

(Culex group). 

Wing scales broader than in Ciilex ; male palpi 
plumose Protoculex 

(Aedes group). 

Female palpi longer than in Culex, scales on 
basal and second antennal segments, male palpi 
enlarged apically dense hair tufts ; of three 

segments Banksinella 

(Aedes group). 

Male palpi of two segments .... Mimeteculex 

(Aedes group). 

Male antennae with special organs . . . Lophoceratomyia 

(Culex group). 

Proboscis hairy in the middle .... Trichopronomyia 

(Culex group). 

Male palpi with an outstanding line of scales Pretinopalpus 

(Culex group). 

Wings with elongated broadish scales. Fork- 
cells long. Brown species. Proboscis banded. Taeniorhynchus 

(Culex group). 

Golden, yellow and purple species . , . Chrysoconops 

(Aedes group). 

Wings with large broad and asymmetrical scales. 

Scutellar scales narrow-curved .... Mansonia 

(Culex group). 

Scutellar scales flat . . . . • . Mansonoides 

(Culex group). 

Wing scales large and fan-shaped . t • Lepidoplatys 

(Aedes group). 

Wing scales heart-shaped . . . : . Etorleptiomyia 

(Culex group). 



GENERA OF SUBFAMILY CULICINAE. THEOBALD 213 



II. Femora and tibiae swollen apically and basally. 
Wing scales small, dense and broad at the 
apices of the veins. Small black gnats 

Wing scales longer and Tacniorhynchus-hke 

Similar, but male palpi shorter than proboscis . 

Abdomen with large flat projecting lateral 
scales, with deeply dentate apices, in more 
or less dense tufts. 

Wing scales of Cttlcx type 

BBB Abdomen with scale ventral tufts, 

Wing scales pyriform, dense and mottled . 

Scutellum nude except for two lines of 
scales. 

Head with small flat scales,, with a 
median line of narrow-curved ones. 

Thorax mostly nude ; scales on scutellum 
long and thin • . . . . 

Head with broad, short curved scales, 
those at sides broader and flatter but 
not spatuate; scutellar scales broadish. 

Near Finlaya but with mid-ventral ab- 
dominal scale tufts . ■ ■ . 

Near Orthopodomyia but male palpi 
longer, Mansonia-\i\e scales on the 
wings and very long scales on the 
male antennae . .... 



Melanoconion 

(Culex group). 
Neomelanoconion 

(Culex group). 
Protomelano- 

conion 



Lasioconops 

(Culex group). 

Finlaya 

(Aedes group). 



Bancroftia 

(?) 

Pneumaculex 

(Aedes group). 

Orthopodomyia 

(Culex group). 



Newsteadina 

(Aedes group). 



II. Eyes \'ery large, completely fused in middle line ; scutellum 

with narrow scales Oculeomyia 

(Culex group). 

Scutellum with flat scales Molpemyia 

(Aedes group). 

III. Eyes small ; scutellum with a large backwardly projecting 

process . . . . > Rachionotomyia 

(Aedes group) . 

The subfamily Heptaphlebomyinae contains the single genus Hepta- 
phlehomyia, Theobald, with three species from West Africa and 
Madagascar. The subfamily Aedinae contains some nine or ten 
genera, a full description of which will be found in Theobald's mono- 
graph. The subfamily Deinoceratinae contains the two genera 
Deinocerites and Dinomimites, |the larvae of which live in crab 
holes. 



214 



MEDICAL ENTOMOLOGY 



Edwards in a recent paper divides the Culicina (sensu lato) into 
two groups, as follows : — 

Culex group. Eggs laid in masses ; the last segment of the abdo- 
men of the female is broad and immoveable ; the claws of the female 
are never toothed. 

Aedes group. Eggs laid singly; last segment of the abdomen of 
the female narrow, usually completely retractile into the penultimate ; 
claws of the female, at least on the four anterior legs, nearly always 
toothed. 

A few of the more important genera of the Culicina will now be 
considered in detail. 

Genus Culex, L. 

The head is clothed UHth narrow curved scales, upright forked 
scales and flat ones at the sides. The palpi are long in the male, 
short in the female ; the scutellum is covered with narrow curved scales. 

Edwards would restrict this genus to those species in which the 
male palpi turn upwards and are longer than the proboscis, the fore 
and mid claws unequal, and the hind simple and equal. He regards 
the following generic names as synonyms ; Heteroncyha, Arrib. ; 
Lasioconops, Theo. ; Melanoconion, Theo. ; Trichopronomyia, Theo. ; 
Neociilex, Theo. ; Pseiidoheptaphlebomyia, Ventr. ; Mochlostyrax, Dj^ar 
and Knab ; Jamesia, Christ. ; Maillitia, Theo. ; Aporociilex, Theo. ; 
Leiicomyia, Theo. ; Microciilex, Theo. ; Oculeomyia, Theo. 

Ctdex fatigans, Wied. (Plate XXXVI, fig. 2). A medium -sized 
species, with a brown thorax marked with indistinct dark lines. 
Abdomen dark with pale creamy bands, and sometimes pale lateral 
spots. Legs dark brown, bases of femora, knee spots, and occasionally 
the apices of the tibiae, pale. Claws of fore and mid -legs of male 
unequal and uniserrated ; the hind claws simple and equal. It is widely 
distributed, and is mainly a house-frequenting species. It is believed 
to be the invertebrate host of Filar ia hancrofti. In Madras, it is 
commonly infected with Herpetomonas culicis, Novy, MacNeal and 
Torrey. 

Genus Taeniorhynchus, Arribalzaga. 

Palpi long in the male and short in the female ; head covered with 
narroiv curved and upright forked scales. Wing scales broad to very 
broad, more or less bluntly pointed. The smaller claw on the fore and 
mid tarsi of the vtale not serrated, a marked characteristic of the genus. 



GENUS STEGOMYIA 



215 



All the species of the genus are of a yellowish colour and most are 
of medium size, though some are large insects. 

Taeniorhynchiis titiUans, Walk. According to Edwards this spe- 
cies should be' the type of Arribalzaga's genus, as it was evidently the 
species described by him in his elaborate description of Taeniorhynchiis. 
This species, together with pseudotitUUans, Theo., is said to act as 
the invertebrate host of FUaria hancrofti. T. titiJlans is a large 
river species corhmon in South America ; it has a brown thorax, 
dark palpi and proboscis, the latter sometimes with a trace of banding ; 
abdomen dusky brown, sometimes with white scales on the sides ; 
the legs are yellowish brown, femora and tibiae without bands, but 
tarsi with basal pale bands. Pseiidofifillans is very like it, but is 
said to be smaller, and more reddish brown in colour, and has yellow 
apical bands on the abdomen. The eggs of most of the species of 
this genus are laid in long masses of two or more rows ; the larva has 
a long- or short-pointed syphon. 

Genus Mansonoides, Theobald 

Mosquitoes resembling those of the last genus, as regards the struc- 
ture of the smaller claiv of the fore and mid tarsi of the male, but 
with the palpi curved upwards as in Culex, and the last joint bent down 
at an angle to the penultimate one. 

Mansonoides uniformis, Theobald. Allied to T. tifillans, but the ab- 
domen has apical lateral pale spots, and the legs are mottled and banded. 
This is a common species in South India, and is also found in many 
parts of the Oriental Region, as well as in the Ethiopian and Australian ; 
it is found in swampy places, and in forests, where several observers 
have noted that it bites viciously; it is believed to be one of the inverte- 
brate hosts of Filaria bancrofti. 

Genus Stegomyia, Theobald 

The mosquitoes of this genus are mainly characterized by the white 
^at scales on the head and scutellum. Palpi long in the male and 
very short in the female. The thorax usually has white spots or bands; 
and the legs are black with white bands. 

The genus Stegomyia belongs to the Aedes group, and is closely allied 
to Ochlerotus, Arrib., but differs from it by the thin male palpi. The 
external genitalia of the female are poorly developed, ^\•hile those of the 
male are large and complex ; the large and small claws of the male may 
be uniserrated or not. - 



216 



MEDICAL ENTOMOLOGY 



The five common species of Stegomyia may be distinguished hy the 
following Key : — 

1 . Thorax with one or more white bands 2 

Thorax with one or more white spots 3 

2- Thorax with two median yellowish parallel lines and a curved 
white line on each side, the markings forming the so-called 
lyre pattern ......... fasciata. 

Thorax black with a median white line .... scutellaris. 

Thorax with a median white line, and in addition, three 

parallel white bands on the pleura ..... pseudoscutellaris. 

3. Thorax black, with three or four white spots . . . SUgens. 
Thorax black, with two white lines at the anterior end, and 

a white spot on each side at the base of the wing . . africana. 

Stegomyia fasciata, Fabr. (Plate XXXVI, fig. 1). Head with dark 
scales at sides, and median double band of white scales. Palpi black, 
thin and long, with two basal white bands in the male ; in the female 
short, and either tipped with white or entirely white. Thorax dark 
brown to black, with whitish stripes simulating the shape of a lyre, 
the two median bands often yellowish; scutellum white. Abdomen 
covered with black scales, the bases of the segments with white scales 
forming transverse bands which extend round to the sides. Legs black, 
femora with silvery knee spots; metatarsi with broad white basal bands; 
the first tarsi of the fore and mid legs with a basal white band, the 
others black ; first three tarsi of hind leg with broad white basal bands, 
the last tarsi pure white. 

Stegomyia fasciata, commonly known as the ' Tiger ' mosquito, is 
the invertebrate host of the parasite of Yellow Fever. When the female 
sucks the blood of a person suffering from this disease during the first 
three days of the fever, it becomes infected, and twelve days later it is 
infective. When once it becomes infective it remains so for the rest of 
its life, and is capable of transmitting the disease to a large number of 
people. It is not yet definitely known whether the parasite can infect the 
eggs, and thus the next generation. The virulent nature of the disease, 
and the great danger of its spreading from its endemic centres in Mexico 
and West Africa, have led to a most exhaustive study of the life his- 
tor}' and habits of Stegomyia fasciata. 

The outstanding fact connected with the habits of this mosquito is 
that it is a true domestic insect, and is seldom, it ever, 

Bionomics of fQ,^j,^(j more than 100 yards from inhabited houses; 
Stegomyia fasciata 

it prefers dark corners, and dark clothes, where it rests 
when not feeding. It frequently enters ships when they are moored 



PLATE XXXVI 




STEGOMYIA FASCIATA : EARLY STAGES 217 



in harbours, and finds suitable hiding places in the holds and 
cabins. It bites during the day-time, especially in the afternoon, and 
occasionally after dark ; Goeldi states that it sometimes bites at 
night like other mosquitoes. Copulation apparently takes place on 
the wing, and the males may often be seen accompanying the fe- 
males ; though they settle on the skin, they do not bite. It is 
generally believed that under natural conditions the female feeds only 
on vertebrate blood, but numerous experiments have been carried out 
to show that both sexes can be kept alive on sweet fluids for long 
periods. Goeldi, for instance, kept specimens alive for as long as 102 
days, but no eggs were laid during this time ; there can, therefore, be 
little doubt that Stegomia fasciata can live under natural conditions 
for a long time without blood ; it is probable, however, that this food 
is necessary for the maturation of the eggs. The female can be 
kept alive for many months, and in nature can probably survive for 
at least six months. 

Eggs are, as a rule, laid from five to sixteen days after the female 
takes her first feed of blood ; Mitchell states that the female may 
feed three times before laying the first batch of eggs. There are 
usually three such batches, but there may be as many as nine ; 
each egg is laid singly, and the total number laid at a time may vary 
from twelve to ninety or more. Goeldi thinks that, as a rule, the female 
lives about fourteen days after laying her last batch of eggs. He found 
that fertilized eggs may remain dormant for as long as 102 days, 
and might be laid even after this long period if the female took a feed 
of blood. 

Stegomyia fasciata is widely distributed, and is found almost in 
every subtropical and tropical port, and from sea-level to 4000 feet 
or more above it. 

The eggs, like those of most species of the genus Stegomyia, are black, 
elongated, and studded with what appear to be small whitish bodies, 
which produce the appearance of a frill ; they hatch 
out in from three to four days, but may take as long as 
eight days. Theobald long ago discovered the important fact that the 
eggs were capable of resisting dessication for a considerable time. 
He was able to hatch out well-formed larvae from eggs which had 
been sent from Cuba in a dry test tube. In this connection Newstead 
has carried out more exact experiments. A batch of eggs which had 
been laid on moist filter paper at Manaos, South America, were first 
dried in the air, and later in a dessicator for twenty-four hours, and were 
28 



218 



MEDICAL ENTOMOLOGY 



then sent to England in a well-corked test tube. He gives the fol- 
lowing data : — 

September 9th to 11th ... Eggs laid in Manaos. 

October 26th ... Eggs reached England. Placed in 

water at a temperature of 23° C 
(73-4° F). 

October 27th ... Twelve larvae hatched during the 

previous night, and one after 
12 hours' immersion. 

October 28th ... Larvae began moulting. 

October 30th ... All larvae completed first moult. 

November 4th . . . Larvae pupated. 

November 7th ... First imago, a male, hatched. It 

lived for six days. 

November 8th ... A male and female hatched. 

In this experiment the eggs remained in a dormant condition for 
about forty-seven days. The incubation period after they were im- 
mersed in water lasted about twelve hours. The larval stage was com- 
pleted in nine days, and the pupal stage lasted three days. 

Francis has shown that the eggs of S. fasciata may remain viable 
as long as six and a halflmonths when they are kept dry ; they will not, 
however, hatch after two years. Peryassu found that after five months 
the eggs would not hatch. All these facts are of the utmost import- 
ance in connection with the spread of Yellow Fever. 

The larva of this mosquito, like that of most of the genus, has a 
long body, and a not very well-defined thorax. The syphon tube is 
short and broad, and about one-quarter the length of the abdomen. 
The antenna has a single spine of medium length on the inner aspect, 
and a few small terminal hairs. The labial plate is described as 
having eleven lateral teeth, and a larger central one ; its lower border 
is crenulated. The lateral combs on the eighth segment have about 
ten serrated spines. The spines on the syphon vary in number, and 
are not a reliable guide ; they are, however, usually about eleven or 
twelve in number. The larvae have the power of remaining for long 
periods well below the surface of water. They are to be found in 
collections of water in buckets, pails, old tins, broken bottles, etc., 
in the vicinity of houses. They are commonly infected with a species 
of Herpetomonas and a spirochaete, both of which are found in the 
Malpighian tubes. 

Stegomyia sugens, Wied. Thorax dark brown, marked with four, 



*rHE METANOTRICHINA 



219 



sometimes six, white spots ; abdomen black ; legs black with white 
bands ; tarsi Y^ith basal white bands, the last tarsal joint of the hind 
leg pure white. This species is widely distributed in the Ethiopian 
region, and, like fasciata, is a domestic insect ; it commonly breeds 
in buckets, roadside puddles, and especially in water which collects 
in holes in rocks ; its larvae are often found in antiformicas.* It bites 
during the day and is often a most troublesome pest. 

Stegomyia africana, Theo. Thorax black with two short intensely 
white bands, directed upwards on the anterior border, and a white 
spot at the base of each wing ; pleura with silvery spots. Abdomen 
brown and unhanded with the exception of the last segment, which 
has two metallic spots. Legs black, hind tarsi with four white bands, 
the third broad and the fourth narrow. This species is common on 
the West Coast of Africa. 

Stegomyia scutellaris, Walk. Thorax black, with a median white 
stripe. Abdomen black with white basal bands. Legs black, tarsi 
with basal white bands, and last tarsus of hind leg pure white. A 
common species in the Oriental Region, abounding in many of the 
Indian ports, where it breeds in earthen pots, wooden tubs, bamboo 
stumps, hollows in the trunks of trees, etc. 

Stegomyia pseudoscutellaris, Theo. Closely allied to scutellaris 
but differs from it in having three white bands on the pleura, and 
those on the abdomen confined to the sides of the segments. It is 
said by Bahr to be the invertebrate host of Filaria bancrofti, and 
other species of filaria, in Fiji, where it is a domestic insect. 

The METANOTRICHINA 

Theobald divides this group into three subfamilies, according to 
the characters of the palpi in the male and female. The metanotum 
is clothed with either scales or bristles, and the head and scutellum 
are covered with flat scales. All the species are found in jungles 
and forests, and it is very doubtful whether any of them are blood- 
suckers ; at least they do not appear to bite man. Many are large 
brightly coloured insects, with irridescent wings. The majority are 
found in South America. The genus Eratmapodites contains a number 
of species from Tropical Africa. For further information the reader 
is referred to Theobald's monograph. 

* Tins filled with water in which the legs of tables are placed in order to prevent anta 
from crawling up. ■ > > ■ , 



220 



MEDICAL ENTOMOLOGY 



The ANOPHELINA 

Mosquitoes for the most part with spotted wings, and assuming a 
characteristic tilted attitude when at rest, the proboscis and palpi being 
in the same plane as the thorax and abdomen. Palpi in both sexes, 
almost without exception, equal in length to the proboscis, and frequently 
spatulate at the tip in the male. Head covered with an abundance of 
upright forked scales, but never with flat scales ; thorax and abdomen 
clothed with many hairs, occasionally with scales, and then usually on 
the last abdominal segments only; scutellum simple, never trilobed ; 
metanotum bare or with a few hairs. 

This group of mosquitoes contains the important species which are 
concerned in the transmission of the parasites of malaria, and it is 
therefore important for the worker to be able to identify them. 

Theobald divides his subfamily Anophelinae into twenty-one genera. 
Alcock, however, considers that many of these cannot be separated 
as distinct genera, and he proposes grouping all under the single 
genus Anopheles, dividing it into seven subgenera as follows : — 

Alcock's Synopsis of the subgenera of Anopheles. 

A. The covering of the scutum consists mainly either of hairs 

or of narrow falculate scales. (In any doubtful case the 

palpi are slender, i. e. not shaggy with outstanding scales) ... 1 

B, The covering of the scutum consists mainly of broadish 

elliptical, commonly recumbent scales .... ... 2 

1. Abdomen either without scales or with some inconspicuous 
narrow scales on the genital lobes and terminal segment, 
or with a tuft of scales on the ventral surface of the 

penultimate segment ....... ... 3 

Abdomen with an outstanding tuft of stift and slender scales 

of extraordinary length on either side of every segment. Christya. 
Abdomen with broad and very conspicuous scales on 
several segments, some of the scales sometimes forming 

regular and outstanding tufts Arribalzagla. 

3, Wings either not spotted at all or having a few dark spots 
formed merely by clumps of scales, or if ' variegated,' 
then there are not more than two distinctly formed colour- 
spots on the anterior edge. (In ambiguous cases, e.g. 
where a spot at the tip of the wing might be reckoned as 

anterior, then the palpi are shaggy) .... ; . . 4 
Wings usually much spotted in contrasted colours, their * 
anterior edge barred or branded with numerous alternate 
dark and lights pots or streaks. (In any ambiguous case 
the palpi are not shaggy). Inconspicuous scales occa- 
sionally present on the terminal abdominal segment and 
genital lobes . , . . i . ■ i • Myzomyla. 



GENERA OF ANOPHELINA 



221 



4. No scales on the abdomen (very rarely there may be a few 

scattered and inconspicuous scales on the genital lobes). Anopheles. 
Abdominal scales present, usually as a small outstanding 
tuft on the ventral surface of the penultimate segment, 
rarely as a uniform covering to the terminal segment Myzorhynchus. 
2. The predominant scales of the head are of the ' upright 

forked' kind (cuneiform) Nyssorhynchus. 

The predominant scales of the head are not ' upright forked' . Chagasia. 

Alcock arranges the species of Myzomyia in two intergrading series 

as follows: — 

a. The covering of the scutum consists mainly of hairs . . Myzomyia. 

b. The covering of the scutum consists mainly of falculate scales. Pyretophorus. 

The species of Nyssorhynchus he arranges in three distinct series as 
follows : — 

a. Abdominal scales present on few of the distal segments . . Nyssorhynchus 

b. Abdominal scales scattered on all the segments . . . Neocellia. 
e. Abdominal scales fairly abundant on all the segments, and 

also in outstanding tufts which may be either lateral or 

ventral Cellia. 

In the subgenus Anopheles, Meig., Alcock includes Anopheles, Ste- 
thomyia and Cyclolepidopteron grabhami of Theobald's monograph, and 
Neostethopheles and Patagiamya of James. 

In the subgenus Myzorhynchus, Blanchard, are included Myzorhynchus 
and Lophoscelomyia of Theobald's monograph. 

In the subgenus Arrihalzagia, Theobald, are included Arrihalzagia, 
Kertezia, and part of Cyclolepidopteron of Theobald's monograph. 

In the subgenus Myzomyia, Blanchard, are included Myzomyia, Felti- 
nella, Neomyzomyia and Pyretophorus of Theobald's monograph and 
Nyssomyzomyia of James. 

In the subgenus Nyssorhynchus, Blanchard, are included Nyssorhyn- 
chus, Neocellia and Cellia of Theobald's monograph ; Calvertina of 
Ludlow, and Christophersia of James. 

In the subgenus Chagasia, Cruz, Alcock includes Chagasia, Cruz, and 
Myzorhynchella, Theobald. 

In the descriptions which follow all the species will be referred to 
under the generic name Anopheles (sensu lato), the more restricted 
genera of Theobald being given in brackets so that the worker can refer 
to Theobald's classification of the genera of the subfamily Anophelinae, 
which is given below. 

Theobald's Table of the Genera of the Anophelinae. 

A. First submarginal cell large. 

I« Antennal segments without dense lateral scale tufts. 



222 



MEDICAL ENTOMOLOGY 



(a) Thorax and abdomen with hair-like curved scales, 
a No flat scales on head, but upright forked ones. 

/3 Basal lobe of male genitalia of one segment. 
1. Wing scales rather large, lanceolate . 
2- Wing scales mostly small, narrow or slightly 
lanceolate ; wings prominently spotted along 
costa ........ 

3. Similar but fourth long vein very near base of 

third ; outstanding scales on prothoracic lobes. 

4. Wings with patches of large inflated scales 

Basal lobe of male genitalia of two segments. 

5. Prothoracic lobes with dense outstanding scales. 
Median area of head with some flat scales ; abdomen 

hairy ; prothoracic lobes mammilated. 

6. Wing scales lanceolate 

(b) Thorax with distinct narrow-curved scales ; abdomen 

hairy. 

7. Wing scales small, lanceolate ; head with nor- 

mal forked scales ...... 

8. Wing scales broad and lanceolate; head with 

broad scales, not closely appressed but not 
forked or fimbriated 

(c) Thorax with hair-like curved scales, and some narrow 

curved ones in front ; abdomen with apical lateral 
scale tufts and scaly venter ; no ventral tuft. 

9. Wing scales lanceolate ..... 

(d) Thorax with hair-like curved scales ; no lateral abdom- 

inal tufts ; distinct apical ventral tuft. Palpi of female 
densely scaly. 

10. Wings with dense large lanceolate scales 

(c) Thorax with hair-like curved scales and some narrow- 
curved lateral ones ; abdomen hairy with dense long 
hair-like lateral apical scaly tufts. 

11. Wing scales short, lanceolate and dense ; fork- 

cells rather short ..... 
(J) Thorax with very long hair-like curved scales ; abdo- 
men pilose except last two segments, which are scaly ; 
dense scale tufts on hind femora. 

12. Wings with broadish, blunt lanceolate scales . 
(g) Thorax and abdomen with scales. 

13. Thoracic scales narrow-curved to spindle 

shaped ; abdominal scales as lateral tufts 
and small dorsal patches of flat scales . 

14. Abdomen nearly completely scaly with long 

irregular scales and with lateral scale tufts . 

15. Similar to Cellia but no lateral scale tufts 

16. Abdomen completely scaled with large flat 

scales as in Culex ..... 

17. Thoracic scales hair-like except a few narrow- 

curved ones in front; abdominal scales long, 
broad and irregular . . . . . 



Anopheles. 



Myzomyia. 

Neomyzomyia. 
Cyclolepidop- 

teron. 

Feltinelia. 



Stethomyia. 

Pyretophorus. 
Myzorhynchella. 

Arribalzagia. 

Myzorhynchus. 

Christya. 
Lophoscelomyia. 

Nyssorhynchus. 

Cellia. 
Neocellia. 

Aldrichinella (Al- 
drichia). 

Kerteszia. 



GENERA OF SUBFAMILY ANOPHELINAE. THEOBALD 223 



IL 



Manguinhosia. 
Chagasia. 



Calvertina. 
Bironella. 



Neostethopheles 



18. Thorax with narrow hair-like curved scales 
and some of them broad straight scales, 
others spatulate on the sides. Abdomen 
covered with fine hairs except the three last 
segments which are covered with scales. 
Tufts of scales on hind femora. Wing 
scales lanceolate ...... 

19. Antennal segments with many densely scaly tufts 
B. 20. Antennae with outstanding scales on the second 

segment, more oppressed ones on the first. 
At least one segment of abdomen with long 
flat more or less spatulate scales 
21. First submarginal cell very small 

To the above must be added the following new genera recently 
created by James : — 

Abdomen with hairs but without scales of any kind. Thorax 
with hairs, and, as a rule, without scales of any kind, but in 
one or two species a few long and exceedingly narrow false 
scales may be present, chiefly on the anterior promontory. 
Thoracic lobes with hairs but without scales. Upright forked 
scales of the head very narrow in their whole length (linear or 
rod-shaped) .......... 

Abdomen with hairs but without scales of any kind. Thorax 
with dorsum -clothed with long, narrow, curved, sharp-pointed 
scales which form on the anterior promontory a thick bunch 
projecting over the neck. Prothoracic lobes with a conspicu- 
ous tuft of rather broad true scales projecting anteriorly. 
Upright forked cephalic scales of the usual broadly-expanding 

type 

Abdomen with the first seven or six segments ornamented with 
hairs only. The eighth segment (sometimes also the seventh) 
and the genital process carry in addition a number of scales 
similar in character and arrangement to those of the group 
Nyssorhynchus . Thorax with the dorsum clothed with hairs 
and narrow-curved, sharp-pointed scales of various lengths and 
quite similar to those of the group Myzomyia. In addition 
there are on each side of the anterior third of the dorsum and 
beneath the angles of the anterior promontory some broader 
blunt-ended scales. Prothoracic lobes without a tuft of 
scales. Head with the usual type of upright forked scales 

Abdomen with the dorsum of each segment thickly clothed 
with hairs and narrowly elliptical and blunt-ended scales 
which are not aggregated together to form tufts of any kind. 
The ventral surface of each segment is devoid of scales 
except that from the apices of six segments in the mid-line 
prominent tufts of long, blunt-ended, scales project directly 
downwards. These tufts resemble the single abdominal tuft 
present in the genus Myzorhynchus. Thorax clothed with 
rather narrow oblong and blunt-ended true scales. Prothor- 
acic lobes with a prominent tuft of true scales. Head with 
the usual kind of upright forked scales Christophersia. 



Patagiamyia. 



Nyssomyzomyia. 



r 



224 



MEDICAL ENTOMOLOGY 



Indian Species of Anopheles 

The Indian species of Anopheles have been more thoroughly studied 
than those of any other country, and in James and Liston's Monograph, 
the second edition of which has recently appeared, the worker will find 
an accurate guide to the identification of the known species. Stephens 
and Christopher's pioneer work on the larvae of the Indian species is 
also worthy of note. The descriptions which follow are, in the main, 
taken from the works of the above authors. Many of the papers 
published in' Paliidism have also been consulted. The synoptic table 
prepared by Major Christophers, I. M.S., which is issued by the Central 
Malarial Bureau, Kasauli, will be found most useful, and is the easiest 
one to work with. 

Synoptic Table of Indian Anopheles (females) 
I. Wings unspotted. 

a. Palpi unhanded. Tarsal joints unhanded. 

Anterior forked cell douhle the length of the posterior. 

Head scales very narrow linear , , . . aitkenii 

Anterior forked cell only slightly longer than the post- 
erior. Head scales very narrow, linear, not broadly 
expanded as in most Anopheles , brown mosquito. culiciforniis< 

Head scales expanded and forked as in most 
Anopheles. Hill species, large or moderate 
greyish, black mosquito. ..... barianensis. 

b. Palpi banded, tarsal joints banded .... immaculatus. 

II. Wings spotted. 

A. Tip of hind legs white. 

a. Legs not speckled. (Note 1), 

1. Two or three tarsal segments completely white. 

(Note 2). 

Wings more black than white. Costal 

spots white on dark ground. Spots small fuliginosus. 

Wings more light than black. Scales on 
abdominal segments except the first . , fowleri. 

Wings more light than black. Costal spots 
black on light ground. Spots very distinct, ptilcherrima. 

2. One tarsal segment only completely white. 

(Note 2). Four broad white bands on palpi 

(including apex) karwari. 

b. Legs speckled. (Note 1). 

1 . Two or three tarsal segments completely white, 
(Note 2). 



INDIAN SPECIES OF ANOPHELES 



223 



Palpi with four distinct bands. Beware 
'of speckling imitating fourth band. 
(Note 1.) Speckling of legs generally 
indistinct ...... 

Palpi with three bands including apex. 
Beware of speckling imitating fourth band. 

Palpi prominently speckled. (Note 3.) Palpi 
with two broad apical bands, one narrow 
basal. Three hind tarsal segments com- 
pletely white. Leg speckling pronounced. 

Palpi not speckled. 

Three hind tarsal segments completely 
white. One broad apical palpal band, 
two narrow. Leg speckling not very 
pronounced ...... 

Two hind tarsal segments completely white. 
Broad white band above this. Palpi with 
two broad apical, one narrow basal band 

2. One tarsal segment or less, completely white. 
(Note 2.) 

There may be white tarsal banding as well. 

Palpi with four well marked white bands 
(beware of speckling imitating fourth band). 

Half last tarsal segment white. Black ventral 
scale tufts visible to naked eye. Three 
spots on sixth longitudinal vein. 

Extreme tip of last tarsal segment only 
white. Five or six spots on sixth longi- 
tudinal \'ein. 

Tibio-tarsal joints of hind legs broadly 
banded white , , , , , 

Tibio-tarsal joints not broadly banded white . 

Palpi with three bands (including apex) 
Tip of palpi white. 

Many scales on abdomen .... 

Scales only on last few segments . 

Tip of palpi black ..... 

B. Tip of hind legs not white. 

a. Legs not speckled. 

1» Hind tarsi banded (joints light). 
Palpi unhanded. 

Wings more black than white. White spots small , 
Wings more light than black. Spots large and distinct. 
Hill species 
Palpi with distinct bands. 

Tip of palpi black 

Tip of palpi white. 

Front tarsal joints broadly banded. Brown mosquito. 
Front tarsal joints not broadly banded. Numerous 
fringe spots. Dark species. Third long vein light. 

29 



pulcherrima. 



maculipalpis. 



jamesi. 



theobaldi. 



halli. 



elegans. 
punctulata. 



willmori. 

maculatus, 

indica. 



barblrostris. 
gigas. 
turkhudi. 
rossii. 

jeyporiensis. 



226 



MEDICAL ENTOMOLOGY 



A single fringe spot. Lighter species. Tliird long 

vein dark culicifacies. 

Palpi with narrow bands. 
Wings more black than white. White spots small . nigerrimus. 
Wings more light than black. Spots large and 

distinct. Hill species sitnlensis. 

2. Hind tarsal joints not banded. 

Palpi unbanded, broad white band on femur. Hill 

species lindesayi. 

Palpi banded. 

A single fringe spot. Third long vein dark . . culicifacies. 
Numerous frings spots. Third long vein light. 
Tip of palpi white. 

Narrow almost hair-like scales on thorax.. Stem of 

second long vein mostly dark ..... listoni. 
Broad scales on thorax. Stem of second long \-ein 

mostly light nursei, 

Tip of palpi black. 
Narrow almost hair-like scales on thorax. Stem of 

second long vein mostly dark ..... turkhudi. 
Broad scales on thorax. Stem of second long vein 

mostly light nigrifasciatus. 

b. Legs speckled (Femora and tibiae spotted). 

L Palpi with four well marked white bands (Beware of 
speckling imitating fourth palpal band). 
Tibio-tarsal joint of hind leg forms broad white conspi- 
cuous band ........ elegans. 

Tibio-tarsal joint of hind leg without broad white band, punctulata. 
2. Palpi with three well marked bands. Beware of speck- 
ling imitating fourth band. 
Palpi with two broad apical and narrow basal bands. 
Palpi speckled. Scales on nearly all abdominal 
segments ......... Stephens!. 

I^alpi with one broad apical and two narrow bands 
palpi not speckled. Scales confined to last segment 

or so ludlowi. 

In using the above key Christophers draws attention to the following points : — 
Note 1 . — Speckling on the legs means spotting or banding of the femur and tibia, 
(not banding of the tarsal joints.) Speckling is if present distinct. A faint mottling is 
not considered as speckling. 

Note 2. — Tarsal segments completely white are counted from the tip, stopping at the 
first dark band. If the tip is white, for from 1/12" to J", two or three segments are pure white. 
If the amount of terminal white is very small, one or less segments only are white. 

Note .3. — Speckling on the palpi refers ta white spots on the dorsal surface, usually 
between the middle and basal palpal band. 

Species entered in more than one place ,may show sometimes one appearance and 
sometimes another (e. g. tarsal banding in culicifacies) or an appearance may be o\-er- 
looked (e. g., the rriinute poiijt of. white on the extreme tip of the hind tarsi of 
punctulata.) In either case the table will work out correctly. 

Anopheles (Nyssomyzomyia) rossii, Giles. (Plate XXXVII, fig. 1.) 
Palpi brown with three white bands, the apical being the broadest. 
Thorax fawn coloured. Abdorrien brown. Legs brown, the distal ends 
of the femora, tibiae, and all the tarsal segrnents except the last, with 



I 

r 

{ 



INDIAN SPECIES GF ANOPHELES 



227 



narrow white bands. Costa of wing with six or seven black spots, the 
three first small and often joined. Upper surface of egg with a broad 
frill round it; floats arising from the fringe and touching its margin. 
Larva with frontal hairs simple and unbranched ; palmate hairs from 
second to seventh abdominal segments ; leaflet very long and as a rule 
with a single serration. 

This species is distributed almost throughout India, and has been 
found at a height of 5,000 feet ; it is also common in the Straits Settle- 
ments, Sumatra, Java, and the Philippine Islands. It is essentially a do- 
mestic insect, and breeds as a rule in shallow pools, washings from houses, 
in paddy fields and even in the backwaters along the Madras Coast; it is 
common throughout the year. As far as is known at present it plays no 
part in the transmission of malaria in nature, though it can be infected in 
the laboratory. In a recent paper Bentley shows that rossii is refractory 
to malarial infection in nature. Vogel, working in Java, suggests that 
only adults which were bred from larvae living in salt water become 
infected ; this statement is, however, disproved by the experiments of 
Stephens and Christophers, for these observers were able to infect adults 
which were bred out of larvae living in fresh water. 

Christophers records a variety of rossii from the Andaman Islands 
which has a broader white apical band on the palps ; it is probably 
identical with Anopheles indefinita, Ludlow. It breeds in small and 
temporary collections of water among houses, and appears to be 
restricted to the vicinity of human dwellings. 

Anopheles {Nyssoinyzomyia) liidlowi, Theobald. Palpi with three 
white bands as in rossii, but the apical band is narrower. Thorax dark 
brown with light areas. Abdomen clothed with golden brown hairs. 
Legs speckled and with white bands at all the tarsal joints. Costa with 
six or seven black spots like those of rossii; the basal spots are sometimes 
longer. Its egg, according to Christophers, has a narrow frill and in 
general appearance simulates that of fuliginosus. 

Liidlowi is found in Bengal, Burma, the Andaman Islands and the 
Philippine Islands. In the Andamans, where Christophers has de- 
monstrated it to be a carrier of the parasites of malaria, it is never 
found more than a quarter of a mile from salt water. The larvae 
were found in brackish water near embankments, and in one instance 
Christophers notes the water contained about four per cent of salt. 

Anopheles (Nyssoinyzomyia) punctiilata, James and Listen. Palpi 
with four white bands and speckled on basal half ; the apical band is 
narrow, the next two broad, and the fourth narrow. Thorax clothed 



228 



MEDICAL ENTOMOLOGY 



with hairs and narrow scales. Abdomen also covered with hairs, and 
with a few scales on the last segment. Legs speckled, first tarsi of fore 
and mid legs with a distal white band. Costa with seven dark spots, 
the smallest at the base ; apex of wing with white scales. Egg, larva 
and pupa unknown. This species has been found in the Central Provin- 
ces, at Karwar, at Parel in the Bombay Presidency, in Delhi and in the 
Andaman Islands. Its habits are unknown. It is possibly identical 
with Anopheles (Cellia) punctulata, Donitz. 

Anopheles {Neomyzomyia) elegans, James. Palpi with four white 
bands, the apical band the broadest. Thorax brown to grey, with dark 
longitudinal lines and eye spots. Abdomen brown with dark hairs. 
Legs brown with white speckling, a broad white band at the junction 
of the tibiae and metatarsi of hind legs. Costa with four large black 
spots, and sometimes two or three small basal ones. Egg unkno\\n. 
Larva with simple median and external frontal hairs ; palmate hairs 
only present on the abdominal segments, leaflet with short stumpy 
filament. This species is found in Karwar, and in the Andaman Islands, 
where, according to Christophers, it breeds in rocky mountain streams 
in the forest. 

Anopheles (Neostethopheles) aitkeni, James (in Theobald). Palpi dark 
without any bands. Thorax dark brown. Abdomen black with long 
hairs. Legs brown, without any bands or spots. Wing unspotted ; first 
submarginal cell almost double the length of the second posterior cell. 
Egg unknown. Larva with median frontal hair branched into fork-like 
prongs ; external hairs simple and short. Palmate hairs on second to 
seventh abdominal segments ; leaflets long with short spear-like filaments. 
This species occurs at Karwar, and on the Frontier of Goa, in the Ben- 
gal Duars, and in the Andaman Islands. Its habits are unknown. 

Anopheles {Neostethopheles) culiciforniis, James and Liston. Palpi 
brown, without bands. Thorax clothed for the most part with brown 
hairs. Abdomen brown, covered with golden hairs. Legs long, un- 
handed. Costa without any spots. Egg unknown. Larva with simple 
and unbranched frontal hairs, the external ones short, the median long and 
close together. A long hair with a swollen end and a tuft of fine hairs 
just behind each antenna. Palmate hairs present on thorax and all 
abdominal segments ; leaflet long and pointed, like a thorn, and without 
any definite filament. A long unbranched hair on the side of the third 
abdominal segment. This species is found at Karwar in the Bombay 
Presidency. When resting on the wall its attitude is like that of Ciilex, 
Its habits are unknown. 



PLATE XXXVIIi 




INDIAN SPECIES OF ANOPHELES 



229 



Anopheles {Patagiamyia) lindesayi, Giles. Palpi black, without any 
bands. Thorax black with a large dorsal rectangular whitish area. 
Abdomen black with long hairs. Legs black with a long white band at 
the middle third of the hind femora. Costa almost entirely dark, with a 
characteristic yellow spot at the apex. Egg unknown. Larva with 
simple and unbranched frontal hairs ; antenna with a small branched 
hair. Palmate hairs absent on thorax, well developed on second to 
seventh abdominal segments ; leaflet long with a moderately pointed 
filament. This is chiefly a hill species and is found in Simla, Murree, 
and other hill stations in India. 

Anopheles {Patagiamyia) gigas, Giles. According to Giles, James and 
Listen, the palpi are brown and unhanded. Thorax with a dark rim of 
chocolate colour and a large rectangular area on dorsum. Abdomen broad 
with golden hairs. Legs light brown, with pale bands at the tarsal 
joints. Costa with four black spots, two small basal and two long 
median and apical ones. Egg and larva unknown. This species was 
first recorded from Coonoor, Nilghiri Hills, South India; it has been 
taken by one of the authors at Kodaikanal, Pulney Hills, South India, 
while feeding on a horse during the day. It is a wild mosquito, and was 
never seen in a house in Kodaikanal. 

Anopheles (Patagiamyia) simlensis, ]a.mes. Closely allied to ^/^crs, and 
only differs in having banded palpi. According to James and Listen the 
larva of simlensis has simple and unbranched frontal hairs ; a small 
branched hair on the antenna ; palmate hairs are present on the third to 
the seventh abdominal segments, and the leaflet is short with a stumpy 
filament. 

Anopheles (Myzomyia) culicifacies, Giles. (Plate XXXVIII, fig. 1.) 
Palpi with three small yellow bands of equal size, the tip forming one of 
the bands. Thorax yellowish brown with a dark median line. Abdo- 
men brown with yellowish brown hairs. Legs dark brown, with small 
yellowish spots at the joints. Costa with five black spots, the basal spot 
being the smallest. Egg (Plate XXXIV, fig. 10) with a narrow rim on 
the upper surface, the floats not extending up to it. Larva with simple 
unbranched frontal hairs ; palmate hairs present on the thorax and 
all the abdominal segments ; each leaflet serrated and with a moderately 
fine filament. This species is widely distributed in India, and is 
found in the Punjab throughout the hot weather, but to a much less 
extent in the colder months ; it is common in many parts of Bengal, 
the United Provinces, Bombay, the Central Provinces, Berars, Burma 
and the Madras Presidency, especially in Ennur and the Jeypore Agency 



230 



MEDICAL ^:NT0M0L0GY 



tracts. The larvae are found in pools of rain water, paddy fields, borrow 
pits, pools in dry river beds, and in fact almost any collection of 
natural or artificial water ; it also breeds in wells. 

It is one of the most important natural carriers of the parasites of 
malaria. The mature insects are somewhat difficult to detect, and 
when in dark corners may escape observation, their ciilex-like attitude 
being very deceptive. A variety punjabensis is recorded by James and 
Liston, and is said to differ from the type ciilicifacies by the complete 
absence' of the fourth dark area on the costa and first long vein. 

Anopheles {Myzoinyia) listoni* Liston. Palpi with three white 
bands, one situated at the tip. Thorax yellowish brown, with a 
median and two indistinct lateral lines. Abdomen very dark, almost 
black, with some yellowish white hairs. Legs broad and marked like 
those of ciilicifacies, except that the light patch at the apex of tibia is 
nearly always absent. Costa with four black spots, basal spot as a rule 
not divided into two as in ciilicifacies. Egg with the upper sur- 
face narrow, divided into two parts, each with a narrow frill; floats long 
with about twenty crinkles, and not encroaching on the upper surface. 
Larva wit-h simple and unbranched frontal hairs ; palmate hairs on thorax 
and all abdominal segments ; leaflet moderately long and serrated, and 
with filament similar to that of ciilicifacies. This species is com- 
mon in the Berars, Central Provinces, Bengal Duars, Jeypore Agency, 
Goa, Bombay, Hyderabad (Deccan,) and the North Canara District. 
Theobald states that it occurs in Ceylon and Perak. 

It breeds in running streams, and is probably a natural carrier of 
the parasites of malaria wherever it occurs. It is often difficult to 
distinguish it from ciilicifacies ; James and Liston in their monograph 
state that the length of the first submarginal and first posterior 
cells are the best means of separating the two species. If the first 
submarginal cell is more than half as long as the second posterior, the 
specimen is listoni, if the reverse it is ciilicifacies. 

Anopheles (Myzomyia) leptomeres, Theobald, is, according to James 
and Liston, a variety of listoni. 

Anopheles (sensu restricto) harianensis, James. Palpi black with- 
out any bands. Thorax dark brown. Abdomen almost black, dorsal 
surface of each segment with greyish white areas. Legs broad, coxae 
and trochanters white, otherwise unhanded. Costa without spots. 

* It appears that when describing this species under the name listoni, Major Liston 
believed he was deaUng with listoni, Giles, which is now known to be a distinct species. 
Major Liston's description, therefore, holds priority. 



INDIAN SPECIES OF ANOPHELES 



231 



Early stages unknown. It is found at Barian in the Murree Hills 
in the Punjab. Its habits are unknown. 

Anopheles (sensu restricto) immaculatus, Theobald and James. Palpi 
with three whitish bands, basal ones narrow, apical band broad. 
Thorax ash grey with a dark median line. Abdomen brown with 
golden hairs. Legs brown, apices of tarsal joints with bands, best seen 
in the hind tarsi. Costa without spots. Early stages and habits 
unknown, and the male has not been recorded. It was found at Ennur 
near Madras, by Stephens. 

Anopheles (sensu restricto) tiirhhudi, Liston. Palpi with three white 
bands, apices black. Thorax brown with a median light rectangular area. 
Abdomen olive green, with golden hairs ; legs brown with yellow 
patches at the apices of the femora and tibiae. Costa with six black 
spots, two situated near the base. Egg bullet-shaped, one end more 
rounded than the other ; the upper surface with a rudimentary rim near 
the rounded end ; floats entirely wanting. Larva with simple and 
unbranched frontal hairs, and a posterior one on each side, unbranched 
and projecting over the oral cavity between the frontal hairs ; palmate 
hairs only present on the fourth to the seventh segments ; leaflet long, 
spear-shaped, serrated, and without any free filament. The larva rests 
at the surface of the water in a culex-\\ke attitude. This species is 
common in the Berars, Central Provinces, Kashmere, and in the Punjab. 
It breeds chiefly in clear pools, especially in pools in dry river beds, 
during the rains. It is not known to be a natural carrier of the parasites 
of malaria, but it can be infected in the laboratory. 

Anopheles {Pyretophorus) jeyporiensis, James. Palpi with three white 
bands ; the apical one, which includes the tip, is broader than the others. 
Thorax with somewhat dark lines. Abdomen dark brown with golden 
hairs. Legs dark, with very small clear white bands at all the joints. 
Costa with six black spots, the basal one small. Egg unknown. Larva 
with frontal hairs thickly branched, and a posterior one, also branched, 
between them ; palmate hairs present on thorax and abdominal segments, 
not unlike those of listoni but broader, with the filament much shorter. 
It is found in the Jeypore Agency in the Madras Presidency, also in the 
Central Provinces and in several parts of South India. The larvae 
are usually found in streams, and in irrigation channels in rice fields. 

Anopheles {Pyretophorus) nigrifaciatus, Theobald. Palpi with three 
white bands, the apices black. Thorax ash grey in the middle, and 
brown at the sides. Abdomen brown with golden hairs. Legs brown, 
unhanded. Costa with four large black spots and two smaller ones. 



232 



MEDICAL ENTOMOLOGY 



Egg and larva unknown. The species is fairly common in Quetta af 
certain times of the year. Mrs. Davys says that it breeds in open pools, 
and irrigation channels. 

Anopheles {Pyretophonis) ntirsei, Theobald. Closely allied to nigri- 
fasciatiis ; palpi with a well-marked apical white band. According 
to Mrs. Davys it is one of the commonest anophelines in Quetta, and 
breeds in the same kind of places as nigrifasciatiis ; the larvae are 
able to remain as long as eight minutes below the surface. 

Anopheles (Nyssorhynchtis) maciilatiis, Theobald. Palpi with three 
white bands, the apical one including the tip, and only separated from 
the next by a narrow dark band. Thorax brown with lighter sides. 
Abdomen dark brown. Legs brown and speckled ; the last tarsal 
segment of the hind leg is entirely white. Costa with four long black 
spots, and three smaller basal ones. Egg with frill interrupted by the 
floats, \\ hich touch the upper margin ; floats short, about one-third the 
length of egg. Larva with simple and unbranched frontal hairs ; 
palmate hairs present on second to seventh abdominal segments ; leaflet 
moderately long, filament very short. This species is common in the 
Bengal Duars. 

Anopheles (Nyssorhynchiis) fiiliginosiis, Giles. (Plate XXXVH, fig. 2.) 
Palpi black with three white bands, the basal one narrow, the next 
broader, and the apical one, which includes the tip, broad. Thorax dark 
brown. Abdomen dark, almost black. Legs black, narrow, with distinct 
bands at the fore and mid tarsal joints ; last three tarsi of hind leg 
pure white. Costa with six long black spots separated by small white 
spots. Egg (Plate XXXIV, fig. 8) with rather broad upper surface and 
well-marked frill, which is encroached on by the floats. Larva with 
frontal hairs with few branches, the external with more than the 
internal. Palmate hairs only present on the abdominal segments ; leaflet 
moderately long, serrated and with a long spine. 

This species is widely distributed, and is common in Calcutta and 
other parts of Bengal, in many parts of the Punjab, in Bombay, Goa, 
and the Central Provinces ; it is also common in many places in 
South India, including Madras City. It breeds in pools, ponds and 
tanks with vegetation at the sides, and is a natural carrier of the 
parasites of malaria. 

Adie has noted a distinct but unnamed variety, in which the palpi have 
four narrow white bands, and the last two and a half or two and three- 
quarters of the hind tarsal segments are white. It is found at 
Ferozpore and Amritsar in the Punjab, but only at certain seasons. 



INDIAN SPECIES OF ANOPHELES 



233 



Another variety nagpori, James and Listen, is found in the Central 
Provinces and in the Punjab. The palpi are black tipped, and two 
and one-third tarsal segments of the hind leg are white. 

Anopheles (Nyssorhynchiis) jamesi, Theobald. Palpi black with 
three white bands, the apical band including the tip, and broader than 
the others. Thorax black, clothed with short white scales. Abdomen 
black with whitish scales. Legs light brown and speckled, four tarsal 
bands on fore and mid legs ; in hind legs last three tarsal seg- 
ments pure white. Costa with six black spots, the two basal ones 
being small. Larva with branched frontal hairs. Palmate hairs on 
the first to the seventh abdominal segments, rudimentary ones on the 
thorax. This species is common in Bengal, Central Provinces, and 
in parts of South India ; it is occasionally seen in Madras City. 

Anopheles (Nyssorhynchiis) maciilipalpis, James and Liston. Palpi 
black, with three white bands, and specks of white between them. 
Thorax black, clothed with white scales. Abdomen dark with a 
white sheen. Legs black, spotted all over, the last three and a part 
of the second hind tarsi pure white. Costa with four black spots, 
and two smaller ones near the base. Egg with a narrow rim, floats 
arising from it, but not altering its contour. Larva with frontal 
hairs thickly branched. Palmate hairs or the thorax as well as the 
abdominal segments ; leaflets moderately long with a medium-sized 
pointed filament. This species is found in the Central Provinces, 
Bombay Presidency, South India, and at Drosh in Chitral. 

Anopheles (Nyssorhynchiis) theobaldi, Giles. Palpi with three white 
bands, the apical one including the tip, the basal band very narrow. 
Thorax black, with cream coloured scales and white hairs. Abdomen 
black with white hairs. Legs dark and much speckled, last two 
segments of hind tarsi pure white. Costa with six black spots, the 
basal one small. Larva with slightly branched frontal hairs. Palmate 
hairs rudimentary on the thorax but present on all abdominal segments ; 
leaflet moderately long, filament very short and blunt. This species 
is found in the Berars, Central Provinces, Jeypore State, and Karwar 
in the Bombay Presidency. It breeds in streams. 

Anopheles (Nyssorhynchiis) karwari, James. Palpi with four white 
bands, the apical one including the tip. Thorax dark, almost black, 
with snowy white scales. Abdomen black with golden scales. Legs 
dark without any speckling, except on the fourth and fifth tarsal 
segments of the fore and mid legs ; all the others have distal white 
bands ; the tibiae and all the tarsal segments of the hind legs have 
30 



234 



MEDICAL ENTOMOLOGY 



white bands at their distal ends, the third and fourth segments also 
at their proximal ends ; the last segment is entirely white. Costa 
with one large, three medium sized, and two basal small black spots. 
Larva with frontal hairs simple and unbranched. Palmate hairs absent 
on the thorax. This species is found in Karwar and Goa and most 
probably in other parts of the Bombay Presidency ; it is also common 
at certain seasons in the Bengal Duars ; Leicester records it from 
Malay-. 

Anopheles (Neocellia) indica, Theobald. Palpi dark, with three white 
bands, the apices dark. Thorax with a frosty sheen. Abdomen brown 
to black, legs with femora, tibiae, and all the first tarsal segments 
spotted ; second tarsal segment of hind leg with a broad white band, 
the third and fourth with bands at both ends, and the fifth entirely 
white. Costa with six black spots, the two basal ones small. This 
species is found at Dehra Dun and other places at the foot of the 
Himalayas. 

Anopheles {Neocellia) uulliiion, James. Palpi black, with three white 
bands, the apical one including the tip. Thorax greyish brown. Ab- 
domen dark, covered with white scales and hairs. Legs dark brown, 
extensivel}^ speckled with white spots ; the distal end of the second hind 
tarsal segment has a broad white band continuous with a similar band 
on the upper end of the third segment, the third and fourth segments 
have broad apical and basal bands, and the last segment is entirely 
white. Costa with four large and three small basal black spots. The 
egg is of the lisfoni type, the upper surface being narrow. Larva with 
simple and unbranched frontal hairs, and a well developed posterior 
hair. Palmate hairs well marked from the third to the seventh seg- 
ments, rudimentary on the second ; the leaflet is moderately long, ser- 
rated, and has a short filament. This important species is widely dis- 
tributed in the Punjab and Kashmir ; it is found at Pathankot, and in the 
Kangra valley, where Mrs. Adie has found it infected with sporozoits ; 
it is common at Murree, Almorah, and in parts of Chitral. It breeds 
in streams and clear pools. 

A variety maculosa, James and Listen, is said to be abundant at the 
foot of the Himalayas ; it differs from the type in having several white 
patches between the two proximal palpal bands in addition to the usual 
markings. 

Anopheles (Neocellia) stephensi, Liston. (Plate XXXVIII, fig. 2.) 
Palpi with three white bands and some intermediate white patches ; the 
apical band is broad and includes the tip. Thorax light brown, sometimes 



INDIAN SPECIES OF ANOPHELES 



235 



much darker. Abdomen dark brown. Legs brown, speckled and 
not conspicuously banded, the last tarsal segment of the hind leg is 
entirely dark. Costa with six black spots, the two basal ones small. 
Egg (Plate XXXIV, fig. 2) with a broad upper surface, the floats arising 
from the rim. Larva with simple and unbranched frontal hairs. Pal- 
mate hairs only on the abdominal segments ; leaflet long and pointed, 
very similar to that of I'ossii, but rather shorter. This species occurs 
almost all over the plains of India ; it has been recorded from the 
Punjab, Bengal, Bombay, Central Provinces, the Berars, Sind, Assam, 
and South India. It is an important natural carrier of the parasites of 
malaria. Bentley, who has made a careful study of its habits in Bombay, 
notes that it is a domestic species, breeding in wells and cisterns, 
in collections of fresh water of every kind, in brackish water, and 
water that contained more salt than sea water. Larvae which hatch 
out in fresh water die when placed in salt water, but those which hatch 
out in salt water live and develop into mosquitoes. The larvae are able 
to remain twenty minutes under water. In Madras this species breeds 
in both used and disused wells in the town ; the authors found numbers 
of larvae in a well which was in constant use by no less than four 
families. In Mian Mir it breeds in tins of water. 

Anopheles (Cellia) piilcherrima, Theobald. Palpi brown with four 
white bands, the apical one broad and including the tip. Thorax dark, 
with three longitudinal rows of white scales. Legs dark and speckled, 
the last three and a half and sometimes three and three-quarters of the 
hind tarsal segments entirely white. Costa with six black spots, the 
basal ones small. Egg much the same as that of stephensi, but the rim 
is much broader. Larva with simple and unbranched frontal hairs. 
Palmate hairs absent from the thorax ; leaflets moderately long, the 
filament very long. This species is common in many parts of the 
Punjab, the North-West Frontier, and the Bombay Presidency. The 
larvae have been found in rain pools. 

Anopheles (Myzorhynchiis) barhirostris, Van der Wulp. Palpi dark, 
heavily clothed with scales, but without bands. Thorax dark, with some 
silvery scales. Abdomen brown. Legs dark brown without any true 
bands. Costa with a small patch of white scales at the junction of the 
apical and middle thirds, and another at the apex. Larva with a branch- 
ed hair on the inner side of the antenna ; median frontal hairs simple, 
occasionally forked ; external hair branched, forming a cockade. Palmate 
hairs present on the second to the seventh segments ; leaflets short 
and broad, filament short. This species is found scantily in most parts 



236 



MEDICAL ENTOMOLOGY 



of the plains of India ; Cliristophers records it as occurring in swarms in 
the forest regions of the Andaman Islands, where it attacked viciousl)'. 
It seems hardly ever to come into houses, and may be considered a 
sylvan species. 

Anopheles (Myzorhynchiis) sinensis, Wiedemann. Palpi dark with 
four white bands, the apical one including the tip. Thorax dark, cloth- 
ed with yellowish scales. Abdomen covered with yellowish hairs. Legs 
brown- with small white bands at all the joints. Costa almost entirely 
black, except for two small white spots, one at the junction of the mid- 
dle and apical third, the other near the apex of the wing. Larva with 
the median frontal hair forked, external hairs branched and forming a 
cockade ; the antenna has a large branched hair on the inner side ; pal- 
mate hairs are only present on the abdomen ; leaflet long, lance-shaped 
and serrated, filament short and stout. This species is common in 
Bengal, Punjab, Bombay, and the Madras Presidency. The larvae are 
generally found in pools of water away from houses. According to 
James and Liston, Anopheles {Myzorhynchiis) nigerriiniis is identical 
with sinensis. 

Anopheles (Neocellia) fowleri, Christophers. Palpi black with a broad 
apical band, and two narrow pale bands dividing the palps into three 
equal areas. Thorax black, covered with creamy white scales arranged 
in rows. Abdomen clothed with light coloured hairs and creamy white 
scales. Legs brownish, first to third tarsal segments of fore legs apically 
banded, the last two segments black. Pale bands on apex of first two 
tarsal segments of mid legs, the last three segments dark. Costa with 
four dark spots, the third from the apex of the wing the longest, and two 
small basal spots. This species resembles fuliginosiis, but is of a lighter 
colour. Its larva also resembles that of fuliginosiis, but the median 
frontal hairs are more branched. Palmate hairs absent on the thorax 
and the first abdominal segment ; the second has undeveloped ones. 
The filament is half the length of the stem of the leaflet. The larvae 
are found in rice-fields, in borrow pits and in tanks, but not in flowing 
water. The imagines are very common in certain parts of the Central 
Provinces during the cold weather. 

Anopheles {Christophersia) halli, James. Palpi clothed with white 
scales, forming five broad white bands, separated by four narrow black 
bands. Thorax brown with dark eye-like spots. Abdomen light brown. 
Legs dark and speckled with clear white spots ; the third, fourth and 
fifth hind tarsi have white basal and apical bands. Costa with five dis- 
tinct black spots, and some small indistinct ones near the base. This 



MALAYAN AND PHILIPPINE SPECIES OF ANOPHELES 237 



species is found in Sylhet, Assam. Its larva has a stumpy appearance ; 
the median frontal hairs are simple and widely separated ; the external 
ones are simple and very short, arising from papillae close to the bases 
of the median hairs. Palmate hairs present on third to seventh seg- 
ments ; leaflet of moderate length. 

Malayan and Philippine Species of Anopheles 

Anopheles (Stethomyia) fragilis, Theobald. Palpi dark and without 
bands. Thorax brown. Abdomen brown or almost black. Legs brown 
and unhanded. Costa dark without spots. A small species found in 
the jungles near Kuala Lumpur, Federated Malay States. It breeds in 
jungle pools, and has a resting attitude like that of Ciilex. 

Anopheles (Myzorhynchiis ; Patagiamyia) separatiis, Leicester. Palpi 
with three white bands, the basal ones indistinct, the apical one includ- 
ing the tip. Thorax brown. Abdomen brown. Legs brown with in- 
distinct bands at first three tarsal joints. Costa with two small spots. 
From Kuala Lumpur. 

Anopheles {Myzorhynchiis) peditaeniatus, Leicester. From the Malay 
States ; considered by James and Stanton to be a variety oi^sinensis 
(see page 236). 

Anopheles (Myzorhynchiis) minutus, Theobald. From the Malay 
States and India, also considered by James and Liston to be a variety of 
sinensis. 

Anopheles (Lophoscelomyia) asiaticiis, Leicester. Palpi dark, un- 
handed. Thorax brown. Abdomen greenish yellow. Legs brown 
with a characteristic tuft of long scales at the joint between the hind 
femora and tibiae. Costa with two well-marked yellow spots. From 
Kuala Lumpur. 

Anopheles (Myzomyia) alhirostris, Theobald. Palpi with two broad 
yellowish white apical bands, and a much narrower one at the basal 
third. Thorax slate grey in middle, brown at sides. Abdomen brown 
with golden hairs. Legs brown with minute spots at the joints. 
Costa of wing black with three almost equal yellow spots, and a very 
small one near the base. From the Malay States. According to 
James and Stanton, it is a common species on some of the rubber 
plantations at Kuala Lumpur, where it has been found naturally 
infected with the parasites of malaria. 

Anopheles {Myzorhynchiis) alhotaeniatus, Theobald. From the 
Malayan Region. It is similar to alhirostris but said to differ from it as 
follows : — the first segment of the hind tarsus has narrow white basal 



238 



MEDICAL ENTOMOLOGY 



and apical bands, the second and third are broadly banded at both 
ends, and the last tarsus is entirely white. It is found at Perak. 

Anopheles (Myzomyia) deceptor, Donitz. Palpi white from about 
the middle of the second joint, with dark rings at the bases of the 
third and fourth joints. Costa with four dark spots, and a very small 
fifth one at the base of the wing. From Sumatra. 

Another species A. {Myzomyia) leuchophynis, Donitz, is in all 
probability the Indian elegans. 

Anopheles (Cellia) kochi, Donitz. Palpi yellow and black at the base, 
followed by a small ring of white and black scales, then a band of 
yellow followed by two broad bands of white, the last joint being 
pale yellow. Thorax pale brown with frosty tomentum. Abdomen 
brown with golden hairs. Legs speckled, and banded, last three tarsi 
of the fore and hind legs yellow. Costa with four black spots. From 
Malay and the adjacent parts. 

Anopheles (Cellia) piinctiilatiis, Donitz. Almost identical with kochi, 
and only differing in having the tarsi clearly banded. From Malay 
and the adjacent parts. 

Anopheles (Stethomyia) pallida, Ludlow. Palpi unhanded, wings 
without spots, but in all other respects like A. fragilis (see above) ; the 
thorax is said to have a frosty grey tomentum. 

Anopheles (Stethomyia) formosits, Ludlow. Palpi brown with three 
white narrow pale bands, the apical one including the tip. Thorax 
with yellowish stripes. Abdomen greyish brown with light yellow 
hairs. Legs brown with narrow bands at the tarsal joints. Costa 
with four brown spots, the two at the base being smaller. From the 
Philippine Islands. 

Anopheles (Myzomyia) thorntoni, Ludlow. Palpi with four white 
bands, the basal one narrow, the apical one broad and including the tip. 
Costa with four black spots and one or two minute ones at base. 
From Mindanoa, in the Philippine Islands. It is related to the Indian 
elegans (see page 228). 

Anopheles (Pyretophoriis) minimus, Theobald. Palpi with four white 
bands. Legs brown and unhanded. Costa black with three distinct 
almost equal yellow spots. From the Philippine Islands and China. 

Anopheles (Nyssorhynchiis) philippinensis, Ludlow. Palpi with four 
white bands, the apical one including the tip. Legs unhanded. Costa 
with two small and four large brown spots. From the Philippine Islands. 
This species comes very near the Indian fuliginosus, only differing in 
the markings on the wings and the absence of speckling on the legs. 



AUSTRALIAN SPECIES OF ANOPHELES 239 



Anopheles (Pyretophoriis) freerae, Banks. Palpi with two white bands, 
one including the tip, and often a few pale spots near the base. Fore 
and mid legs with banded tarsi ; posterior tarsi snow white. From 
Manilla. 

Anopheles {Calvertina) Uneatiis, Ludlow. Palpi with three white 
bands, the apical one including the tip. Legs dark, hind metatarsus 
with a white spot at its apex, the next segment has a broad white apical 
band, and all the remaining joints are pure white. Costa with four 
small white spots, and a smaller fifth one at the tip. From the 
Philippine Islands. 

Anopheles {Cellia ; Nyssorhynchiis) flavus, Ludlow. Palpi almost 
white with four yellowish bands, the apical one broad, and including 
the tip. Costa with seven or eight dark brown spots, four of which are 
large, and two basal ones. From the Philippine Islands. 

Anopheles (sensu restricto) treacheri, Leicester. Said by James and 
Stanton to be identical with the Indian aitkeni (see page 228). 

Anopheles {Myzomyia) aurirostris, Watson. Palpi brown ^^•ith four 
white bands. Thorax and abdomen brown. Legs brown and unhanded. 
A small species from the Federated Malay States. 

Anopheles {Nyssorhynchiis) nivipes, Theobald. Palpi brown with two 
white bands or patches on ventral surface. James and Stanton record 
having seen the female, though up to the present the male alone has 
been described. According to these observers it is closely related to 
the Indian fitliginosiis ; it is found in Mala}'. Christophers records a 
local variety from the Andaman Islands, and has found its larvae in 
rice fields close to a sea embankment. 

Australian Species of Anopheles 

Anopheles (Nyossrhynchiis) annulipes, Walker. Palpi brown, with 
four white bands, the proximal one broad, the basal narrow. Thorax 
of a slate brown colour with a central line of yellowish scales. Ab- 
domen brownish black, clothed with j'ellow hairs. Tarsi with apical 
and basal pale bands. Costa with four black spots. Widely distributed 
in Australia and Tasmania, where it is believed to be the chief natural 
carrier of the parasites of malaria. It is also found in Formosa, where 
Kinoshita has demonstrated that it is suitable host for the parasites of 
malaria. 

Anopheles (Myzorhynchtis) bancrofti, Giles. Palpi black and un- 
handed. Thorax black with golden brown scales. Abdomen black 
with brown scales. Legs black, the tarsi with small apical pale 



240 



MEDICAL ENTOMOLOGY 



bands. Costa black with two white spots. A large dark species widely 
distributed in Queensland. 

Anopheles (sensu restricto) corethroides, Theobald. Palpi dark brown 
and unhanded. Thorax pale brown with a large median dark area in 
front. Abdomen deep brown. Legs brown and unhanded. Costa with- 
out any spots. This species is found in South Queensland. 

Anopheles (sensu restricto) atratiis, Skuse. Palpi dark, with light 
patches at the apices. Costa with six dark spots. Legs unhanded. It 
is found in South Queensland. 

Arabian Species of Anopheles 

Anopheles (sensu restricto ?) arabiensis, Patton. Palpi with three white 
bands, the distal one including the apex. Thorax brown. Abdomen 
clothed with brown hairs. Legs dark brown with yellowish bands at 
all joints. Costa with seven dark spots, four long and three short. 
Egg boat-shaped, frill well marked, the floats not encroaching on it. 
Larva with simple and unbranched frontal hairs ; palmate hairs present 
on the second to the seventh segments ; the leaflet is long and serrated, 
the filament long and pointed. 

This species is extremely common in the Aden Hinterland, breeding 
in pools and along the edges of the smaller rivulets ; it is also common 
near Sheik Othman, nine miles from Aden, where it breeds in wells. 
It was found by the senior author to be naturally infected with the sporo- 
zoits of the parasite of malaria. Mr. Theobald states that it does not 
belong to any of his genera, but up to the present he has not created a 
new genus for its reception. The type of this species and of the others 
described below were unfortunately lost with some baggage in the Aden 
Hinterland. 

Anopheles {Myzomyia) d'thali, Patton. Palpi with two white bands. 
Thorax yellowish brown. Abdomen greenish with dark patches. Legs 
brown, faint bands at all the joints. Costa with four black spots, the 
basal one the longest. Egg boat-shaped with a narrow frill deeply 
encroached upon by the floats, which almost meet in the middle line. 
Larva with simple and unbranched frontal hairs ; palmate hairs well 
developed from first to seventh segments ; leaflet long and serrated more 
on one side than the other, filament long. Mr. Theobald thinks it is 
Anopheles nili. 

Anopheles (Nyssorhynchits) tibani, Patton. Palpi with three white 
bands, the apical one broad and sometimes divided into two. Thorax 
dark with silvery scales. Abdomen clothed with dark hairs. Legs dark 



EUROPEAN SPECIES OF ANOPHELES 241 



and banded, two and a half to two and three-quarters hind tarsi pure 
white. Costa with six white spots, the median one the longest. Egg 
with a narrow frill, floats extending up to it but not encroaching on it. 
Larva with simple and unbranched frontal hairs ; palmate hairs from the 
second to the seventh segments ; leaflet serrated more on one side than 
on the other, filament long. It breeds in all the rivers and springs in the 
Aden Hinterland, as far up as Jehaf (6,800 feet), and about ninety miles 
inland from Aden. 

Anopheles {Myzomyia) jehafi, Patton. Palpi with four white bands, 
the last including the apex. Thorax and abdomen brown. Legs 
brown with pale areas at all the joints. Costa with six black spots. 
Egg boat-shaped, without a frill or floats, and thus unlike the typical 
anopheline egg ; like that of Stegomyia, it will hatch after sinking in 
water. Larva with simple and unbranched frontal hairs ; palmate hairs 
present on the third to the seventh segments ; leaflet long, deeply 
serrated ; filament long and pointed. This species breeds in springs 
and wells. 

Anopheles {Myzomyia) azriki, Patton. Palpi with three bands, apices 
dark. Thorax and abdomen brown. Legs brown, without bands. 
Costa with five black spots. Larva with simple and unbranched frontal 
hairs ; palmate hairs present on fourth to seventh segments ; leaflet 
short and broad, and serrated ; filament with a short spike. It was found 
in the Aden Hinterland, breeding in a spring. 

European Species of Anopheles 

Anopheles (sensu restricto) maculipennis, Meigen. Palpi brown, un- 
handed. Thorax and abdomen brown. Legs brown, without any 
definite bands. Costa dark with four dark spots, two apical and two 
median. It is widely distributed in Europe, and is a natural carrier 
of the parasites of malaria in Italy. 

Anopheles (sensu restricto) hifurcatiis, L. Palpi unhanded. Thorax 
chestnut brown. Abdomen dark brown, with some short golden hairs. 
Legs brown and unhanded. Costa and wing itself without any spots. 
Europe. 

Anopheles (sensu restricto) nigripes, Staeger. Palpi black and un- 
handed, but sometimes with traces of light bands. Thorax and abdomen 
blackish brown. Legs deep brown, without bands. Costa black without 
spots. Europe. 

Anopheles {Myzorhynchiis) psetidopictus, Grassi. Palpi brown, with 
31 



242 



MEDICAL ENTOMOLOGY 



three white-scaled bands. Thorax and abdomen dark. Legs brown, 
apices of metatarsi and tarsi with narrow pale bands. Costa with two 
light spots at its apex. Italy and some other parts of Europe. 

Anopheles {Myzomyia) hispaniola, Theobald, and Anopheles {Pyre- 
tophonis ?) siiperpictus, Grassi, from Spain and the neighbouring Islands, 
and from Southern Europe, are described on pages 250 and 251. 

Anopheles {Pyretophorns) cardatnatisi, Newstead and Carter. Palpi 
long and thin, with three white bands, the apical one of which is the 
broadest. Thorax greyish brown with whitish scales. Abdomen brown 
with pale hairs. Legs brown with light markings at the joints. Costa 
with six black spots, the three basal ones small. From Athens. 

NORTH AMERICAN SPECIES OF ANOPHELES 

Anopheles (sensu restricto) punctipennis, Say. Palpi with two in- 
distinct greyish bands, and apices sometimes grey. Thorax chestnut 
brown. Abdomen brown with golden hairs. Legs brown, except 
coxae, knees and tips of tibiae, which are yellowish. Costa black, 
with two yellow spots, one at the apex and the other at the apical 
third. This species is the winter anopheline of the United States. 

Anopheles (sensu restricto) perplexans, Ludlow. Palpi dark with 
white tips. Thorax with a broad white median stripe, and covered 
with white frost. Abdomen dark brown. Legs with extremities of 
femora and tibiae yellowish. Costa with one small yellowish spot, 
and a second one at its junction with the first longitudinal vein. 
From Pennsylvania. 

Anopheles (sensu restricto) franciscaniis, McCracken. Palpi with 
three indistinct pale bands. Legs without any distinct bands. Costa 
with two yellow spots. From California and Texas. 

Anopheles (sensu restricto) crucians, Wied. Palpi with three white 
bands, the last one including the apex, which is silvery grey. Legs 
brown, with tips of femora and tibiae yellowish, Costa with one 
yellow spot. Widely distributed in North America, where it is a 
common species. 

Anopheles (sensu restricto) barheri, Coquillett. This is the 'tree- 
hole' anopheline of the United States; it commonly breeds in the 
water which collects in hollow trees. Theobald thinks it is very 
near the European bifiircatiis (page 241). It is found in Maryland 
and New Jersey. 



AFRICAN SPECIES OF ANOPHELES 243 



Anopheles (sensu restricto) occidentalis, Dyar and Knab. Palpi, ab- 
domen, and legs, brown. Thorax with a broad band on dorsum, cut 
across by three narrow stripes. Wing with four black spots. From 
California, San Diego, and Oregon. 

Anopheles (sensu restricto) at ropes, Dyar and Knab, and Anopheles 
(sensu restricto) quadrimaculatus, Say, are probably only varieties of 
A. maculipennis. 

In addition to the above, A. maculipennis, A. hifurcatus, and 
A. nivipes are found in parts of North America. 

AFRICAN SPECIES OF ANOPHELES 
Edward's Key to the Species 



1. Thorax with distinct broadish-elliptical scales (except in 

A. Christy i) ; female palpi shaggily scaled ; abdomen usually 

more or less scaly .......... t 2 

■ Thorax clothed with hairs, or narrow almost hair-like scales ; 
scales of female palpi usually appressed ; abdomen with- 
out scales on the dorsal surface . 13 

2. Abdominal scales obviously present on all the segments .... 3 
Abdominal scales absent, or if present, confined to the terminal 

segments (' Nyssorhynchus ') . 8 

3. Abdominal scales forming distinct projecting lateral tufts 

[Nyssorhynchus, [ = Cellia]) ......... 4 

Abdominal scales not forming tufts (Neocellia) ...... 9 

4. Last joint of hind tarsi light, or at least light-tipped 5 

Last joint of all tarsi entirely dark ........ 7 

5. Last joint of fore and mid tarsi all dark ; rather light yel- 

lowish species (5 to 6 mm) ...... pharoensis. 

Last joint of fore and mid tarsi light or light-tipped ; smaller, 

less yellow species (4. 5 mm. or less) .... ... 6 

6- Last joint of all tarsi wholly yellow ; remaining joints 
regularly ringed with black and yellow ; very small species 

(3 mm) cinctus. 

Last joint of all tarsi white tipped ; remaining joints not 

ringed ; larger species jacobi. 

7. Hind tarsi entirely dark argenteolobatus. 

First four joints of hind tarsi with equal white rings . squamosus. 

8. Last tarsal joint white; small species (3.5 mm) ; Egyptian maculicosta. 
Last tarsal joint not white ; large species (7 mm) ; East 

African christyi. 

9. Hind tarsi entirely dark ; three white palpal bands in female, 

the first two narrow brunnipes. 

Last two or three joints of hind tarsi white 10 

10. Four narrow white palpal bands ; wing scales lanceolate ; legs 

spotted aureosquatniger 



244 



MEDICAL ENTOMOLOGY 



Three palpal bands, the two last rather broad ; wing scales 

much narrower ............ 1 1 

11. Femora and tibiae white-spotted . . . . . . . . . 12 

Femora and tibiae not white-spotted ..... rufipes. 

12. Palpi white-spotted maculipalpis. 

Palpi not white-spotted pretoriensis. 

13. Abdomen with lateral tufts of very long slender scales on each 

segment {Christya) , . implexus. 

Abdomen without lateral scale tufts . . . . . . . . 14 

14. Wing scales mostly yellow, the black patches on the veins 

much reduced, but three long and one short black marks on 

the costa and first vein, the first two almost or quite united . . . 15 
Wings not so marked ........... 16 

15. Last 2i joints of hind tarsi white theileri. 

Last joint of hind tarsi dark wellcomei. 

16. Wings with at least three pale spots on the costal border 

(doubtful species are included in the next division, 

[Myzomyia]) ............ 17 

Wings with at most two pale spots on the costal border .... 36 

17. Last hind tarsal joints white ; legs spotted .... natalensis. 

Last hind tarsal joints not white . . . . . , . . . 18 

18. Femora and tibiae more or less spotted with white; tarsi dis- 

tinctly ringed at the joints .......... 19 

Femora and tibiae not at all white-spotted ....... 20 

19. Hind metatarsi with about five well-marked narrow whitish 

rings ; female palpi with four narrow white rings . . ardensis. 
Hind metatarsi without distinct rings ; female palpi with three 

white rings, the apical one broad ..... costalis. 

20. Third vein with three dark and two light areas ; male palpi 

with the club mainly yellow, as in costalis . . pallidopalpis. 

Third vein with only two dark areas (near base and apex), or 

entirely dark ............ 2 1 

21. Palpi of female white only at the apex ; base of first fork-cell 

nearer apex of wing than that of second ; small, very dark 
species . . . ... . . . . nili. 

Palpi of female with three or four white rings ...... 22 

22. Third vein mainly, (ftmestus, type form, and culicifacies) or 

entirely dark ; mesonotum clothed with hairs ...... 23 

Third vein mainly pale ........... 26 

23. Hind tarsi with fairly distinct pale rings ; wing field with some 

pale spots longipalpis. 

Legs entirely dark . . . . . . 24 

24. Wing field entirely dark ; no pale scales even at bases of fork- 

cells rhodesiensis. 

Pale spots present at bases of fork-cells, even in the darkest 

specimens 25 

25. Lighter species, Mediterranean and Oriental . • . . . culicifacies. 
Darker species (very variable), Ethiopian .... funestus. 

26. Palpi of female black-tipped 27 



Palpi of female white-tipped (in A . cinereus the white scales 
at the tip are easily rubbed off) ; mesonotum with narrow, 
but fairly distinct scales ...... . 



AFRICAN SPECIES OF ANOPHELES 



245 



27. No dark scales on first fork-cell or on anterior branch of 

second impunctus- 

Dark spots present (though sometimes small) on first fork-cell . . . 28 

28. Vestiture of mesonotum consists of hairs ..... hispaniola. 
Vestiture of mesonotum consists of narrow scales ...... 29 

29. Third and fourth costal spots smaller ; first fork-cell mainly 

pale-scaled cliaudoyei. 

Third and fourth costal spots larger ; first fork-cell mainly 

dark-scaled multicolor. 

30. Last joint of female palpi mainly dark, pale at each end ; 

large species, wing length about 5 mm. .... cinereus. 

Last joint of female palpi mainly or entirely white . . . . . 31 
3L Tarsi dark ; middle ring on female palpi rather narrow ..... 32 

Tarsi with pale articulations .......... 33 

32- Average wing length 3.8 mm transvaalensis. 

Average wing length 3 mm. . ...... funestus. 

33. Larger (about 5 mm.) ; Mediterranean ..... superpictus. 
Smaller ; Ethiopian ; middle and terminal pale rings on 

female palpi about equal and rather broad ; tarsal joints 

with narrow yellowish rings ......... 34 

34. Larger, darker species (3.5 to 4.5 mm) ; third and fourth costal 

spots larger marshal li. 

Smaller, lighter species (3 to 3.2 mm) ; third and fourth costal 

spots smaller . . . . . . . . . . . .35 

35. A dark spot at apex of wing pitchfordi. 

No dark spot at apex of wing ....... f lavicosta. 

36. Thorax clothed with narrow scales ; light spots on wing more 

numerous . . . . . . . . . ' . . 37 

Thorax clothed with hairs (excluding the scales near the front 

margin) ; wings very dark, or else quite unicolourous .... 39 

37. The two last palpal bands (in female) about equal and rather 

broad — as in ntarshalli ; tarsal joints with rather broad 

white apical rings ........ austeni. 

Palpi of female with four narrow whitish rings ; the terminal 

joint having a dark ring in the middle ....... 38 

38. Numerous yellow-forked scales on the head ; legs dark, tarsi 

scarcely ringed distinctU5. 

No yellow-forked scales on head ; femora and tibiae spotted 

with whitish, tarsi distinctly ringed at the joints . . . costalis var. 

melas. 

39. Last 2 to 3 joints of hind tarsi white ; female with a tuft of 

scales on the ventral side of the last abdominal segment 

[Myzoyhynchus] muritianus. 

Last joints of hind tarsi not white ; female without ventral 

scale-tuft ............. 40 

40. Blackish species ; wings with some pale spots . . . . . . .41 

Lighter species ; wings without any pale spots ...... 42 

41. Female palpi shaggily scaled ; pale scales of wings occurring 

mainly on the fourth, fifth and sixth veins .... umbrosus. 
Female palpi with appressed scales ; pale scales of wings less 

numerous and occurring mainly on the first vein . . . smithii. 

42. Wings with dark spots formed by accumulation of scales. maculipennis. 



246 



MEDICAL ENTOMOLOGY 



Wings without any dark spots ......... 43 

43. First fork-cell longer than the second ..... algeriensis. 
Fork-cells of equal length ....... antennatus. 

Anopheles (Cellia) pharoensis, Theobald. Palpi brown with two 
narrow white bands, and white tip, elsewhere mottled with white. 
Thorax brown, with a dark median line and a fawn coloured stripe on 
each side ; abdomen brown, densely covered with yellowish hairs and 
scales, and with lateral tufts of darker scales. Legs with femora and 
tibiae banded and mottled, metatarsi and tarsi with broad apical white 
bands ; last tarsal joint white. Costa with three dark spots, the middle 
one the largest, the two others small. A distinct and very widely dis- 
tributed African species. Recorded from Palestine, Egypt, Soudan, 
Gambia, North and South Nigeria, Togo Land, the Belgian Cogo, An- 
gola, Southern Rhodesia, Delogoa Bay, and Madagascar. 

Anopheles {Cellia) cinctus, Newstead and Carter. Distinguished 
from the above and allied forms by the rings on the metatarsi of the 
middle and hind legs ; only one specimen is known, from Ashanti. 

Anopheles {Cellia) jacobi, Hill and Haddon. A large black and white 
species with spotted legs. Palpi black, with an incomplete white band 
near the base, a narrow band about the middle, and an irregular white 
band at apex. Thorax sepia with three white longitudinal bands, as well 
as three on pleura. Abdomen thickly covered with yellow scales and 
hairs, and with lateral tufts of black scales on second to seventh seg- 
ments. Legs dark grey, spotted with white ; metatarsi and all tarsi 
except the third of the fore and mid legs with white bands ; the last 
tarsi of all legs white. Costa with three small white spots, a fourth at 
the apex, and two small spots at the base. The larva, which lives in 
springs, is large and deeply pigmented ; antenna without a branched hair 
on the shaft, but with a small spine on the external aspect. Frontal 
hairs branched ; palmate hairs absent on thorax, rudimentary on iirst 
abdominal segment, better developed on second, and prominent on third 
to seventh segments ; leaflet broad. This species is found in South 
Africa. 

Anopheles {Cellia) argenteolohatiis, Gough. Palpi dark, with three 
white bands. Thorax dark, with a large eye-like spot on each side of 
the median line. Abdomen dark brown. Legs brown, unhanded. 
Costa black with three large white spots and two smaller ones. It is 
found in the Transvaal and North-East Rhodesia. Edwards considers 
that Anopheles pseiidosquaniosiis, Newst. and Cart., is identical with it. 

Anopheles {Cellia) squaniosus, Theobald. Palpi dark, with two nar- 
row white bands and white apex. Thorax dark, with white scales 



AFRICAN SPECIES OF ANOPHELES 247 



arranged in lines ; pleura with three white lines. Legs dark, speckled with 
white ; apex of first and second tarsal joints of fore and mid legs with 
broad white bands ; metatarsi of hind legs with apical bands, as well as 
the next three tarsal joints, the last black. Costa jet black, with three 
distinct white spots, one smaller at apex and two at base. This is a 
dark species, widely distributed in Africa ; it has been recorded from 
Egypt, Sudan, Northern Nigeria, Sierra Leone, Gold Coast, Angola, 
Natal, Transvaal, Rhodesia, Nyasaland and British East Africa ; it also 
occurs in Madagascar. 

Its larva is slender with a pigmented median stripe. Antenna without 
a branched hair, terminal spines equal. Frontal hairs consisting of three 
pairs, the external dendriform. Palmate hairs rudimentary on the tho- 
rax, well developed on the first abdominal segment, large on the second 
to seventh ; leaflets narrow and few in number. The larvae are found in 
springs and marshes. 

Anopheles (CeUia) maciilicosta, Becker. This species is considered 
by Edwards to be a worn specimen of A. pharoensis. From Egypt. 

Anopheles {Neocellia) christyi, Newstead and Carter. Palpi brown 
with two white apical bands, and a narrow creamy basal one. Thorax 
almost black, with cream coloured scales. Abdomen very dark, with 
white basal lateral areas to the middle segments. Legs brown : tarsi of 
fore and hind legs dark with broad apical creamy bands, the last seg- 
ment dark. Costa with five black spots, the second and third the 
longest. Wing unusually broad. It is found in Uganda and British 
East Africa. 

Anopheles (Nyssorhynchus) hninnipes, Theobald, Palpi black, with 
two narrow white apical bands and broad white tip, Thorax brown, 
with a dark median line, narrow submedian lines, and two dark spots. 
Legs uniformly brown. Costa dark with three large creamy white 
spots, and two smaller ones near base ; the first fork-cell is very long. 
From Angola. 

Anopheles (Pyretophonis) aiireosqiiamiger, Theobald. Palpi brown, 
with four white bands, one apical and the others lower down. Thorax 
slate grey with characteristic golden spindle-shaped scales. Abdomen 
blackish brown. Legs brown with spots ; first two tarsi of fore leg with 
broad white apical band, the last three of the hind leg entirely white. 
From the Transvaal. 

Anopheles (Nyssorhynchus) ritfipes, Gough. Palpi without spots, but 
with two pale apical bands. Hind legs with narrow white bands, 
apices of tibiae, metatarsi, and first tarsal joints, also third to fifth tarsal 



248 



MEDICAL ENTOMOLOGY 



joints, white ; black band near base of third. This species is closely 
related to A. pretoriensis. It is found in British East Africa, Gold 
Coast, North and South Nigeria. 

Anopheles ( Nyssorhynchus) maciilipalpis, Giles. According to Ed- 
wards, who has re-examined the British Museum specimens, this species 
is identical with the Indian anophelene bearing the same name (see 
page 233). It is widely distributed, and is recorded from the Transvaal 
Rhodesia, Congo and Nigeria. 

Anopheles (Nyssorhynchus) pretoriensis, Theobald. This species 
closely resembles maculipalpis, except that the palpi are not mottled 
with white, and the bands are further apart ; the last two tarsi of the 
hind leg are all white. The larva is said to differ from that of maculipal- 
pis in having the frontal hairs unbranched, the outer very short and the 
median long and thin. It is found in the Transvaal and Natal. 

Anopheles {Christya) implexiis, Theobald. A large species. Palpi 
with three white bands, and white apices. Thorax brown with golden 
yellow scales. Abdomen black with long dense lateral tufts of black 
and golden hairs, the black ones in apical tufts. Legs brown, femora 
and tibiae spotted, third and fourth segments of hind tarsi white, the 
last segment black. A very striking Anopheles, for which Theobald 
erected the genus Christya, of which it is the only species. 

Anopheles {Pyretophorus) thellcri, Edwards {P. alhipes, Theobald), 
No description is given, but it is said to be a very distinct species, 
but in its wing markings almost identical with A. wellcomei (?) Theobald 
(see below). It is found in the Transvaal. 

Anopheles ( sensu restricto) wellcomei, Theobald. Palpi with two 
white bands, one near the apex, and the other about one-fourth the way 
down. Thorax ash grey with a broad dark median stripe. Abdomen 
ochreous. Legs brown with very narrow yellow apical bands. Costa 
with two well marked yellow spots near the apex. From the Soudan, 
Northern Nigeria, and Angola. 

Anopheles (Myzorhnchus) natalensis. Hill and Haddon. Palpi with 
five pale bands including the apex. Costa with three white spots and a 
fourth at the apex. Legs spotted and banded. First hind tarsi with 
broad apical bands, last tarsi two and a half to two and three quarters 
white. Natal. 

Anopheles {Pyretophorus) ardensis, Theobald. Palpi with three nar- 
row white bands and white apices. Thorax greyish brown. Legs brown, 
femora, tibiae, and metatarsi spotted, remaining tarsi with apical pale 
bands. It is found in Natal and is probably only a variety of A. costalis. 



PLATE XXXIX 




AFRICAN SPECIES OF ANOPHELES 249 



Anopheles [Pyretophonis) cosfalis, Loew. (Plate XXXIX, fig. 1.) 
Palpi with two white bands, and yellowish white apices ; a variation 
is often seen in the band at the apex, which may be divided, the 
palp then appearing to have four bands. Thorax brown with a dusky 
median line, and when denuded of scales with five lines. Abdomen 
black with long golden hairs. Legs with femora and tibiae brown, spot- 
ted with white ; the tarsal joints are banded with yellow, especially 
in the fore legs. Costa with four large and two small black spots, 
the two median ones the longest. This species is very widely dis- 
tributed in Africa, as well as in Madagascar and Mauritius; it is a 
natural carrier of the parasites of malaria. The larva has branched 
frontal hairs ; the antenna is without a lateral hair or plume on its 
shaft ; the palmate hairs are present from the second to the seventh 
segments, each leaflet being filamentous. The larvae are commonh' 
found in swampy water, in roadside puddles and in foul pools about 
African houses. 

Anopheles costalis shows considerable variation in its markings, and 
the late Dr. Donitz was of the opinion that Theobald's identification 
of the species is erroneous, and that it is probably A. cinereus, Theo- 
bald; he therefore suggested the name gracilis. 

Anopheles (Felfinella) paUidopalpi, Theobald. Palpi with two 3'el- 
low bands, one of which is apical. Thorax ash-grey with a median 
dark line. Abdomen brown with golden hairs. Legs brown, and 
unhanded. Costa with two pale spots. The genus Feltinella was 
created on the character of the male genitalia, the basal lobe, according 
to Theobald, being divided into two segments. Edwards states that ' the 
type specimen is merely broken.' This species, of which only the male 
is known, is found in Sierra Leone. 

Anopheles (Myzomyia) nili, Theobald. Palpi dark, with one small 
apical band. Thorax fawn coloured. Abdomen black. Legs brown, 
and unhanded. Costa black, with three yellow spots. From the Soudan, 
North and South Nigeria, and Togo Land. 

Anopheles {Myzomyia) longipalpis, Theobald. Palpi with three 
narrow white bands, and white apices. Thorax cinerous. Abdomen 
black. Legs black, hind tarsi and metatarsi with apical and basal yel- 
low bands. Costa dark with four almost equal pale yellow spots. 
From British East Africa, and Nyasaland. 

Anopheles {Myzomyia) rhodesiensis, Theobald. Palpi dark brown 
with three narrow yellow apical bands. Thorax reddish brown. Ab- 
domen brown. Legs dark brown, long and thin, and unhanded. 
32 



250 



MEDICAL ENTOMOLOGY 



Costa with three small white spots, and a yellow spot at apex. This 
species is found in Southern Rhodesia, and in the Transvaal. Ed- 
wards states that it is often confused with Anopheles funestiis. 

Anopheles (MyzomyiaJ ciilicifacies, Giles. Edwards states that, 
after examining a large series of typical ciilicifacies from India, he 
regards A. (Pyretophorus) sergenti, Theobald, as a synonym. For a 
description of ciilicifacies, see page 229. It is found in parts of Algeria. 

Anopheles {Myzomyia) fiinestus, Giles. (Plate XXXIX, fig. 2.) Palpi 
with two white bands and white apices. Thorax dark brown at sides 
and grey in middle. Abdomen blackish brown with light hairs. Legs 
dark brown, metatarsi and tarsi with narrow apical bands, which are often 
absent. Costa with four small yellowish spots, and sometimes two smaller 
ones. Several varieties have been described; A. hehes, Donitz, is 
probably only a variety, and Edwards states that it only differs from 
the type funesfiis in having narrower wings, and pale scales on half 
of the third vein. The varietv siibiiiubrosa, Theobald, has no pale 
spots on the costa near the base, but has some pale scales in the middle 
of the third vein ; the fringe spots are usually distinct. According to 
Edwards, the species A. [Myzomyia) leptomeres, Theobald, is this 
variety. The variety hisignata, Griinberg, has no pale spot near the 
base of the costa, the third vein and sometimes also the fifth are 
entirel}- dark, and the fringe spots are indistinct or absent. 

Anopheles funestus is widely distributed in Africa, being commonest 
in West Africa ; it is a natural carrier of the parasites of malaria. The 
larva has branched frontal hairs ; no hair on the shaft of the antenna. 
The palmate hairs, which are present from the second to the seventh seg- 
ments, are filamentous. They are nearly always found in clear water, 
never in marsh}- or foul pools. 

Anopheles {Myzomyia) impitnctits, Donitz. A little known species and 
of doubtful position ; one specimen was obtained from Egypt. 

Anopheles (Myzomyia) hispauiola, Theobald. Palpi brown with three 
pale bands, the apical one being very small, the greater part of the api- 
cal joint black. Thorax slate-grey with brown sides. Abdomen blackish 
brown, paler below. Legs brown, apices of femora and tibiae pale yel- 
low, tarsi unhanded. Costa with five black spots, the basal part being 
black. Edwards states that A. (Pyretophorus) myzomyfacies, Theobald, 
is a svnonym. It is found in Spain, Algeria, and the neighbouring 
parts. 

Anopheles (Pyretophorus) chaiidoyei, Theobald. Palpi with three 
narrow white bands, the first two nearer one another than the second 



AFRICAN SPECIES OF ANOPHELES 



251 



and with two indistinct median lines. Abdomen dark brown, nearly 
black. Legs brown with traces of bands on the fore and mid tibiae. 
Costa mostly pale, with five or six black spots, all smaller than the 
intervening clear spaces. According to Edwards A. (Pyretophonis) 
nigrifasciatus, Theobald, is a synonym (see page 231). A. chaiidoyei 
is found in Algeria and Cyprus. 

Anopheles (sensu restricto) multicolor, Camboulin. A doubtful species 
described from Suez and Cairo. 

Anopheles {Pyretophonis) cinerens, Theobald. Palpi with four white 
bands, the terminal ones including the apices. Thorax ash grey in the 
middle and dark brown at the sides. Abdomen dark. Legs thin, dark, 
and spotted, last tarsal joints of all legs paler than the rest. Costa black 
with three yellow spots. From British East Africa, Rhodesia, Transvaal, 
Natal and the Cape. 

Anopheles {Pyretophonis) transvaalensis, Carter. A doubtful species 
from East Africa, Transvaal and Natal. Edwards thinks it will prob- 
ably prove to be 4. fiinestiis. 

Anopheles {Pyretophonis) siiperpictiis, Grassi. Palpi with three white 
bands, the apical joint and apex being entirely white. Thorax brown 
with light scales. Abdomen brownish yellow. Legs brown with white 
bands at most of the joints. Costa with four black spots, and one or 
more in addition near the base. It is found all over Southern Europe, 
and along the North African Coast. 

Anopheles {Pyretophonis) marshalli, Theobald. Palpi black, with a 
white apical band, another of the same width close to it, and a smaller 
one near the base. Thorax slate grey, and brown at the sides. Abdo- 
men black with golden hairs. Legs brown, apices of all joints except 
the last tarsal with small yellow bands. Costa with six small creamy 
spots. From Uganda, British East Africa, Nyasaland, Rhodesia, An- 
gola, and the Transvaal. 

Anopheles {Pyretophonis) pitcpfordi, Power, (in Giles). An imper- 
fectly described species with four light spots on the costa. From Zulu- 
land and Uganda. 

. Anopheles {Myzomyia) flavicosta, Edwards. Palpi with three white 
bands, a narrow one near the base, the last, including the tip, broad, 
the intermediate band equally broad. Thorax ash grey with brown sides. 
Abdomen dark brown with golden yellow hair. Costa with four black 
spots, and black at the base. From Northern Nigeria. 

Anopheles {Pyretophonis) aiisteni, Theobald. Palpi with two broad 
white bands, one forming the apex, and a much narrower third band. 



252 



MEDICAL ENTOMOLOGY 



Thorax brown with silvery scales. Abdomen black with golden hairs. 
Legs black with apices of all segments, except the last in the fore and mid 
legs, with narrow white bands. Costa with three white spots, the apical 
one large, the second smaller, and the third very small. From Angola. 

Anopheles (Pyretophonis) distinct us, Newstead and Carter. Falpi 
with four white bands, the apices white. Thorax slate grey with a 
dark median longitudinal line. Abdomen dark brown, with pale 
golden brown hairs. Legs brown, lighter below ; fore legs with narrow 
white apical bands on the metatarsus and first tarsal segments ; 
middle and hind legs with pale areas at the articulations. Costa 
mostly black with two pale spots ; these characters distinguish it from 
any other anopheline. From the Luapala river, North-East Rhodesia. 
A variety meJanocosta is also recorded from the same locality, which 
differs from the type in having the whole of the costa black, with 
the exception of a small pale apical spot. 

Anopheles {Myzorhynchits) niiiritianiis, Grandpre. Palpi with four 
pale bands, the terminal one including the apex. Thorax dark brown 
with dark longitudinal lines. Abdomen black, clothed with brown 
hairs. Fore and mid tarsi with white bands at their apices, hind 
tarsi banded with white apically and basally ; apex of first, most of 
the second, and both the last tarsi of the hind leg banded or entirely 
white. Costa black with two white spots, one near the apex. 
This species is widely distributed in Africa and is said to be the 
commonest anopheline at Nairobi. 

Anopheles (Myzorhynchits) umhrosus, Theobald. Palpi black, without 
any bands. Thorax black with traces of lines and with golden scales. 
Abdomen grey with brown hairs. Legs brown, all joints with pale 
bands. Costa black with a yellow spot at the apex. Found in 
Southern Nigeria, Congo, Cameroon, and the Malay States. Edwards 
states that A. {Myzorhynchits) obscttriis, Griinberg, and A. (Myzorhyn- 
chits) strachani, Theobald, are synonyms. 

Anopheles (sensu restricto) sniithi, Theobald. Palpi black with three 
narrow pale lands, apices black. Thorax grey with a dark median line. 
Abdomen black with brown hairs. Legs brown and unhanded. Costa 
black. From Sierra Leone. 

Anopheles (sensu restricto) inaciilipcnnis, Meigen. This species is 
chiefly European and is described on page 241. It is said to occur in 
Tunis. 

Anopheles (sensu restricto) algeriensis, Theobald. This species is 
probably identical with the European bifurcatus, (see page 241). 



SOUTH AMERICAN AND WEST INDIAN SPECIES 253 



Anopheles (sensu restricto) antennatus, Becker. A species difficult to 
locate and placed as uncertain by Theobald. 

South American and West Indian Species of Anopheles. 

Anopheles (sensu restricto) vesfipennis, Dyar and Knab. Tarsi banded 
with white, hind tarsi black and white. Costa with small yellow spots. 
An imperfectly described species, from Guatemala, Mexico. 

Anopheles (sensu restricto) strigiimaciila, Dyar and Knab. Another 
doubtful species from Cordoba, Mexico. 

Anopheles (sensu restricto) apicimaciila, Dyar and Knab. Said to be 
like the former species, but with a distinct black costo-apical spot on 
wing. It is found in Guatemala, Panama and Trinidad. 

Anopheles (sensu restricto) piinctimaciila, Dyar and Knab, from Colon, 
and Anopheles eiseni (?) Coquillett, from Guatemala are doubtful species. 

Anopheles (sensu restricto) pseiidopiinctipennis, Theobald. Palpi with 
three white bands, the last one including the apex. Legs brown, coxae, 
trochanters and base of femora pale. Costa with two yellowish white 
spots. From Grenada. 

Anopheles (Stethomyia) nimbus, Theobald. Palpi long and thin w ithout 
any bands. Thorax black with a silvery median line. Legs long, thin, 
and unhanded. Wings densely scaled but unspotted. From British 
Guiana, also from Brazil. It simulates a Ciilex when at rest. 

Anopheles {Chagasia) fajardi, Lutz. Palpi with dense dark scales 
and pale rings at the joints. Thorax yellowish white with golden 
sheen. Legs spotted and banded, the bands on the tarsi broad. 
Wings without any spots. When at rest assumes the attitude of 
Ctilex. Egg without floats, ribbed and striated. Larva with simple 
median frontal hairs, external pair branched ; palmate hairs from 
first to seventh segments ; leaflet broad, fan-like ; filament with a 
simple hair projecting from centre. From Brazil. 

Anopheles {Myzorhynchella ; Chagasia) niger, Theobald. Palpi dark 
with four narrow white bands, the two apical ones close together. 
Thorax black with creamy-white scales. Legs banded, apex of hind 
metatarsus, half the second and the last three tarsi pure white, 
Costa with three small yellow spots and two smaller ones at base. 
From Mexico and Brazil. 

Anopheles {Myzorhynchella ; Chagasia) nigritarsus, Chagas. Palpi dark, 
without any distinct bands. Thorax and abdomen dark brown. Legs 
dark, with spots and bands, the last tarsus of hind leg pure white, 



254 



MEDICAL ENTOMOLOGY 



the third and fourth white with black rings. Costa dark with live 
yellow spots. From Brazil. 

Anopheles {Myzorhynchella ; Chagasia) lutzianiis, Chagas. Palpi 
black, with white scales at the apices of the segments. Legs dark, 
with spots and bands, the distal two-fifths of the second and the 
last three white. Costa dark with four yellow spots. From Brazil. 

Anopheles {Myzorhynchella ; Chagasia) parvus, Chagas. Palpi with 
four white bands, the terminal one including apex. The distal half 
of the second hind tarsi and the last three tarsi white. Costa with 
three small white spots. F"rom Brazil. 

Anopheles {Myzorhynchella) fibiamaciilatus, Neiva. Palpi dark with 
about one-third of apical segment white. Legs spotted. Costa with 
two small yellow spots. From Brazil. 

Anopheles {Cyclolepidopteron) mediopiincfatiis, Theobald. Palpi banded . 
with black and gold. Thorax reddish brown with a green sheen, and 
two dark eye spots. Abdomen brown. Legs brown, ^ ith spots and 
bands, the last tarsal joints of all legs yellow. Costa with three well- 
marked black spots. PVom Brazil. 

Anopheles {Cyclolepidopteron) intermedins, Chagas. Only differs from 
the above in having no bands on the palps. 

Anopheles {Arrihalzagia) maculipes, Theobald. Palpi with four white 
bands, the last one including the tip. Thorax brown with slate-grey 
sheen. Legs brown with many spots, and white bands. Costa with 
three black spots. From Brazil and Trinidad. 

Anopheles {Arrihalzagia) pseudoinaciilipes, Chagas. According to 
Chagas it differs from the above in having broader wing scales, and many 
more tarsal spots. P>om Brazil. 

Anopheles {Mangiiinhosia) liitzi, Chagas. Palpi dark with indistinct 
stripes. Legs j-ellowish brown, ends of tibiae white. Costa with two 
large black spots, and one or more smaller ones. From Brazil. 

Anopheles {Kerteszia) boliviensis, Theobald. Palpi with three narrow 
yellow bands, one of which forms the apex. Thorax ash grey, with 
two straight parallel median lines. Legs brown ; two or three tarsal 
segments are spotted or banded. Costa with four yellow spots. From 
Bolivia. 

Anopheles {Myzomyia) lutzi, Theobald. Palpi dark, with three narrow 
white bands, one of which is at the tip. Legs dark and banded, first 
tarsal segment of fore and mid legs banded with dark and white bands ; 
the last three tarsi of fore and hind legs with white tips. Costa with 
.five pale spots. Rio de Janeiro. 



BIONOMICS OF ANOPHELINA 



^255 



Anopheles (Cellia) bigot ii, Theobald. Palpi with four white bands, one 
at the apex. Thorax brown with four greyish longitudinal lines. Legs 
brown, banded ; apical band on metatarsus and first two tarsi of fore legs, 
and last joint white ; last three tarsi and apex of the first of the hind leg 
pure white. Costa dark with three white spots. From Chili. 

Anopheles (Cellia) brasiliensis, Peryassu. Allied to argyrotarsis (see 
below), but the three spots on the wing costa are larger. From Brazil. 

Anopheles (sensu restricto) mattogrossensis, Lutz and Neiva. Palpi 
dark and unhanded. Thorax dark in the centre and yello\\'ish at the 
sides. Abdomen dark with silvery hairs. Legs dark with a bronze sheen, 
with indistinct apical rings to the upper segments. Wing dark with two 
brownish j-ellow spots on the costa. From Lake Mandicore, Motto 
Grosso, Brazil. 

Anopheles {Cyclolepidopteron) grahhaini, Theobald. Palpi densely 
scaled, but unhanded. Thorax slate grey, mottled with brown. Legs 
brown and spotted. Costa black with a yellow spot at the tip of 
the wing. Larva with a characteristic white mark on its thorax ; 
frontal hairs simple and unbranched ; palmate hairs from second to 
seventh segments ; leaflet long and without any definite filament. . From 
Jamaica and Cuba. 

Anopheles {Cellia) argyrotarsis, Robineau-Desvoidy. Palpi with 
three white bands, one including the apex. Legs yellowish, the apex 
of the first tarsus of the hind leg and the last three tarsi white. Costa 
with four large white patches and one or two smaller ones. This species 
is common in the West Indies, and is found in St. Lucia, Antigua, Gre- 
nada, Jamaica Cuba, Haitai, and Porto Rico ; it is also recorded from 
British Guiana, Brazil, and the Argentine. It is an important natural 
carrier of the parasites of malaria. 

Anopheles {Cellia) aibimanus, Wied. This species is almost in- 
distinguishable from argyrotarsis, and can only be separated b}- noting 
that the last segment of the hind tarsus is entirely black, while, except 
for the claws, it is white in argyrotarsis. It is common in man}- parts 
of the West Indies, and in Brazil. It is a carrier of the parasites of 
malaria, and can also act as the host of Filalria bancrofti. It breeds in 
swamps, pools, and in almost any kind of water. 

In spite of the large number of observations which have been made 
during the course of investigations into the etiology of mosquito-borne 
diseases, it has to be admitted that our knowledge of 
the bionomics of the Anophelina, even in the case of ^'"a "^helina 
definitely incriminated species, is far from complete. 



256 



MEDICAL ENTOMOLOGY 



The subject is a difficult one, for a large number of observations must be 
allowed to accumulate before reliable conclusions can be drawn, and 
workers in this field are severeh' handicapped by the difficulty which 
exists in imitating natural conditions sufficiently closely to enable one to 
carry out prolonged and exact experiments with mosquitoes in captivity ; 
the lack of an}- reliable criterion by which the age of any given specimen 
can be judged has also proved a serious obstacle. Although a good deal 
has been ascertained with regard to the breeding habits of the more 
important species, their seasonal prevalence, their mode of spread from 
one locality to another, and the manner in which they tide over the cold 
weather or an unfavourable season, there are many subjects of almost 
equal importance on which our knowledge is very scant)'. Among 
these might be mentioned the relations of the sexes with reference to 
copulation and feeding, the length of life and the conditions which 
determine it, the number of batches of eggs and the time at which each 
is laid, and the choice of host in the different species. Almost all the 
observations recorded have been made on female anophelines, and very 
little is known about the male. 

As the larvae and pupae of the Anophelina are aquatic and free- 
swimming, the essential condition for their breeding is a collection of 

water which will last sufficienth- long to enable them 
Breeding Habits , , . , , i • i • • i 

to complete their earn- stages, and which is either 

stagnant or flows just slowly enough not to wash them away ; food 
material will usually be abundant wherever there is organic matter. 
Such a condition is to be found almost anywhere, but in addition there 
are some subsidiary requirements, more or less peculiar to the species, 
which have to be fulfilled, each species exhibiting a predilection for some 
particular environment, so that out of the half dozen or so Anopheles which 
ma}' be prevalent in any locality, onl)' two or three will be found in the 
same breeding place. The choice is more restricted in some species 
than in others. 

A large number of the Anophelina breed in running water, and the 
larvae of many of the species may be collected from the edges of rivers 
and streams, where they obtain shelter among dead leaves, sticks and 
other debris which collects in such places. In small streams which run 
along dry river beds, and where fresh water collects in pools, larvae can 
usually be found. Many other species breed in rain water puddles, in 
rice fields, in irrigation channels, and in wells and tanks. Several 
species, for instance. Anopheles ludlowi, and Anopheles stephensi, habit- 
ually breed in brackish water, and the latter even in sea water along the 



BREEDING PLACES OF ANOPHELES 



257: 



coast. Anopheles costalis, the commonest West African anopheline, 
though it usually breeds in water holes and roadside puddles, especially 
when fouled by the excreta of man and animals, regularly breeds 
in domestic pots and barrels in native yards in the town of Lagos 
(Graham). Anopheles simlensis and Anopheles willmori, on the other 
hand, prefer to breed in clear mountain streams ; Anopheles titrhhiidi 
is stated by Christophers to breed in river beds in the Punjab, and 
especially in places where water oozes from sand and where there 
is much algal growth. 

The peculiarity of each species is of practical importance from the 
point of view of the prevention of mosquito-borne diseases, and the subject 
has received a due amount of attention. So far as possible the habitat 
of the larva has been given in the account of the individual species. 

Although the Anophelina do in this way show a certain amount of 
choice as regards the places in which they deposit their eggs, they will 
take advantage of any additional collections of water 
which maj- come into existence during the rainy season. Permanent and 
This is a most important point in the epidemiology of ^^'''P"''^^^^^^^''®**''"^ 
malaria, for it is the occurrence of these temporary 
but abundant breeding places which renders possible the great seasonal 
increase in the numbers present in any locality, and the subsequent 
outbreak of an epidemic. 

Bentley in his account of malaria in Bombay, where Anopheles 
stephensi is the incriminated mosquito, draws a useful distinction 
between the permanent and temporary breeding places. In Bombay its 
permanent breeding places are the numerous wells, most of which 
are either actually within the houses or in close proximity to them, 
and also water cisterns, garden tanks, and similar places ; in these 
situations larvae are to be found in small numbers throughout the 
year. During and after the rains, however, stephensi breeds in surface 
pools, tubs, buckets, old earthenware vessels, etc., near the houses, 
and it is to the mosquitoes hatched out in such places that the sudden 
increase in the prevalence of malaria is to be traced. The explana- 
tion of the fact that the larvae are never found in large numbers in 
the permanent breeding places is that the conditions which have 
allowed the species to become established in these situations have also 
permitted of the establishment of their natural enemies, such as preda- 
ceous larvae, small fish, etc., while in the temporary breeding places 
the larvae can grow, and the imagines hatch out, before the natural 
enemies gain a footing; not only do a larger proportion of the eggs 
33 



258 



MEDICAL ENTOMOLOGY 



hatch, but most of the larvae attain maturity and become adults. The 
practical importance of this is evident, for the wells provide a source 
of supply from which the temporary collections of water, which must 
inevitably be formed each year, can be stocked with larvae, and unless 
they are dealt with the appearance of a large number of mosquitoes 
at the time of the rains will continue. 

In the Punjab Christophers has found that the main permanent 
breeding grounds of Anopheles are the large river beds, such as the 
Jumna and Beas, jheels and large tanks filled with aquatic vegetation, 
extensive brick fields and excavated tracts, all of which are common 
around most large towns and even small villages, and lastly the irriga- 
tion channels. After the rains temporary- breeding grounds are formed 
by pits and excavations, and shallow accumulations of rain water. 

Christophers found numbers of the larvae of ctilicifacies and fiiJiginos- 
iis in large sheets of rain water even when there was no obvious 
food. As this water begins to dry up the larvae are to be found in 
the deepest holes, and the next shower of rain enables them to complete 
their development. These extensive collections of water and the resul- 
ting deep pools form the most important temporar}- breeding places for 
the larvae of Anopheles in the Punjab. 

The seasonal prevalence of mosquitoes depends to a large extent, but 
not entirely, upon the presence of suitable breeding places. Sfegoniyia 
fasciata, for instance, occurs all the vear round in 
tropical places with an equable climate ; Ciilex fafigans 
is common throughout the year in Madras, but its numbers are greatly 
increased in November and December after the rains. A marked 
seasonal prevalence has been observed among anopheline mosquitoes 
by workers on malaria in the Punjab. As a general rule all the 
species are most abundant in the latter half of the 3'ear, following on 
the rains in the early part of July, and diminish as the dr}- cold weather 
advances, until there are only a few left in April, when the hot weather 
commences. The season of the 3'ear does not, however, affect the pre- 
valence of all the species in the same way. A. ctilicifacies, for instance, 
disappears entirely during the cold months of the year, and reappears 
as the hot weather approaches, although the number of breeding places 
available by that time is necessarily diminished. James found that in 
Mian Mir it disappeared about the end of November, to return about the 
middle of March or the beginning of April ; in Ferozpore it is absent 
from December to May (Adie) ; at Amritsar it appears in February and 
March, and is to be found, though in gradually diminishing numbers, 



HIBERNATION OF ANOPHELES 



259 



up to the onset of the monsoon, after which it becomes exceedingly 
numerous. A . fiiliginosns, on the other hand, is distinctly the cold weather 
species in the Punjab, and continues to lay its eggs throughout the 
winter ; like culicifacies, it diminishes in numbers with the advance of 
the hot weather, but it does not increase in the same way immediately 
after the rains, the numbers remaining comparatively small until long 
after culicifacies is well established. A. rossii disappears entirely in the 
colder months, and does not reappear till the middle of July. The 
determining factor is probably the optimum temperature for the deve- 
lopment of the larva of each species. 

It should be noted that the nature, as distinct from the amount, of the 
rainfall is important in relation to the prevalence of mosquitoes after the 
rainy season. Continuous torrential rain tends both to wash away the 
larvae and to prevent the females from successfully depositing their eggs. 

Mosquitoes, like all insects which normally have a short life history 

and which can multiply only under certain conditions, are able to exist, 

by one means or another, during unfavourable seasons, 

J ^, ^, 1 J T-u Hibernation and 

m order that the race may be carried on. 1 he com- . . ^. 

. . ... Astivation 

monest manner in which this is brought about is by the 

hibernation of impregnated females, which, finding the season too far ad- 
vanced to complete the maturation and deposition of their ova, seek out 
resting places and remain concealed until favourable conditions present 
themselves at the commencement of the next season. During this period, 
which may extend to many months in temperate climates such as that of 
Europe, they feed seldom if at all, and remain in a passive and torpid 
condition, living upon the store of food material already accumulated, 
until they are revived by the warm weather. The eggs are then laid, and 
it is from these first batches of eggs that the mosquitoes of the ensuing 
season are produced. 

Annett and Button, in the course of their observations on the hiber- 
nation of English mosquitoes, record having found a number of females 
of A. inaciilipennis in cellars, lumber rooms, wash houses and similar 
localities in the month of February. In all these situations the anophe- 
lines were resting in a ciilex-like attitude ; they were difficult to rouse, 
and when caught in a bottle crawled rather than flew into it. They 
never found any of the mosquitoes in stables and cattle sheds, as these 
places were comparatively dry and were constantly warmed by the 
animals at night. Not a single male maculipeiinis was seen throughout 
the observations, which extended over several months in the winter ; this 
fact indicates that it is the female alone which hibernates. 



260 



MEDICAL ENTOMOLOGY 



Similarly many species ' aestivate ' during the hot and dry months in 
the tropics, when, either from lack of water, or because the high tem- 
perature and the dry atmosphere are in themselves unfavourable, the 
eggs cannot be matured and laid. The adults which survive in this 
manner are almost, if not quite, all females. 

In other cases, and particularly in the tropics, adverse conditions 
are met by a retardation of the larval stage. The cold weather does 
not kill off all the larvae, but it inhibits their growth and develop- 
ment, so that this stage may last several months instead of the normal 
period of a week or ten days. When the weather becomes warmer the 
larvae again become active and complete their development ; the imagines 
so produced give rise to successive broods with increased rapidity as the 
weather becomes warmer. It is in this way that cnlicifacies is carried 
over the cold months of the year in the Punjab. 

The eggs themselves, in some species at least, are -able to resist 
unfavourable conditions, such as dryness, for a considerable time ; the 
case of Stegomyia fasciata has already been quoted. Cazeneuve records 
some observations which indicate that they can also resist the action of a 
very low temperature. He succeeded in hatching out eight Anopheles 
larvae from a block of ice taken from a marsh in North China, where the 
temperature frequently falls as low as -32'^ C. 

The question as to the manner in which mosquitoes spread from their 

breeding grounds towards the places where they feed is an important 

one. As a general rule they do not travel far, as they 
Method of Distribu- „ , , r , „ • , r 

tion ^""^ structurally adapted tor long flights or tor 

travelling in rough weather. At times, however, they 

are found at a considerable distance from the nearest breeding places, 

having been either carried there by the wind, or having performed a 

series of short flights on successive days. One of the writers had 

experience of the first method of spread in the Aden Hinterland, where, 

on account of the proximity of infected Arab children and the great 

prevalence of Anopheles, the British and Indian troops were suffering 

severely from malaria. The camp was moved to another place about a 

mile from the only breeding ground, the Wady Tiban, but unfortunately 

it had to be placed on its leeward side. In spite of the distance numerous 

Anoplieles could be found in the tents daily, and the conditions were 

almost as bad as before, although every precaution was taken to prevent 

larvae being brought into the camp in the drinking water. In this case 

the mosquitoes were blown across the open country. 

James records having found gravid females oi fuliginos us in Mian Mir 



DISPERSAL OF ANOPHELES 



261 



at least two and a half miles from the nearest breeding place, and 
Christophers has noted an instance in which male anophelines have flown 
at least four hundred yards. 

In addition to the direct method of dispersal, anophelines may become 
distributed over an area indirectly. All the newly hatched imagines of 
any brood do not necessarily arrive at the same feeding ground as that 
from which the parent came, nor do mature females necessarily return to 
the same breeding place on each occasion to deposit their eggs, or return 
after oviposition to the same house. Starting from any given centre, 
therefore, breeding places may become established along any radius, 
provided that suitable collections of water and food supply are available ; 
each of these secondary breeding places may in turn become a centre for 
dispersal, until eventually the species may be found breeding at a very 
considerable distance from the place at which it originally occurred. At 
Mian Mir, for instance, James found that ciilicifacies was able to spread 
from the surrounding villages into the lines occupied by the British 
troops by means of isolated houses and breeding grounds between the 
two. Such breeding places as are of a permanent nature will serve as 
sources from which surrounding temporary pools may be stocked at the 
proper season. 

In a few cases anophelines are distributed along the ordinary lines 
of transport, in carts, railway carriages, river boats, and from port to 
port in ships. Should the conditions at the place at which they arrive 
be favourable they may become permanently established there. 

Larvae of Anopheles may be carried long distances down irrigation 
channels, in which the flow is intermittent, and those which survive may 
set up new foci. During the anti-malarial operations at Mian Mir the 
larvae of ciilicifacies were found to be transported in this way into areas 
from which the imagines were absent. 

It has already been stated that we are without any reliable cri- 
terion by which the age of a captured anopheline can be judged, or 
by which the number of batches of eggs which it 

has laid can be established. Such a criterion would f*"" u-^'*'"" 

of Anopheles 

be of great assistance in solving many problems Communities 
connected with the bionomics of mosquitoes, and 
in the study of the epidemiology of malaria. The question has been 
attacked recently by Christophers, and although his preliminary work 
has not led to any definite conclusions, the subject is of so much 
importance that an account of it is necessary. 

Christophers, after first describing the development of the ova 



262 



MEDICAL ENTOMOLOGY 



from the early stage up to the time of oviposition, tabulates the 
process and divides the successive changes into five stages as 
follo\\s : — 

Stage 1. Follicle consists of a group of undifferentiated cells. Follicle 
and central cells become differentiated. 
Follicle cells form a distinct epithelium, like cubical 

epithelium. 
Follicle becomes oval. 

Nucleus of the ovum becomes distinguished from those of 
the nurse cells. 
Stage 2. Fine yelk granules appear in protoplasm of ovum. 

Coarse yelk granules appear and increase greatly in number. 

Ovum increases relatively to nurse cells until it occupies 
half the follicle. 
Stage 3. Nucleus is obscured by yelk. 

Ovum occupies ^, f , and respectively of ovum. 
Stage 4. Follicle becomes elongated. 

Nurse cells become less and less conspicuous. 

Follicle assumes shape of mature egg. 
Stage 5. Floats and chitinous structures become visible. 

Egg is laid. 

Since the second follicle commences to develop before the first is 
ripe, the ovary is only found in the first stage in the case of a 
female which is about to develop the first batch of eggs. After 
laying the first batch the ovary is at the second stage, and there- 
after there is nothing to indicate how many batches of eggs have 
already been matured and deposited. Certain other points are of 
assistance in determining the age, or rather in separating the very 
young specimens from the rest. The salivary glands are in an immature 
stage for the first twelve hours of the life of the imago. The 
spermathecae nearly always contain sperms beyond the first stage. 
The mid-gut is practically never free from blood after the first feed 
except when the ova are nearly ripe, and one may conclude, therefore, 
that an anopheline without any blood in its mid-gut and with ovaries 
in the second stage has just laid a batch of eggs, and has not fed 
since it did so. Occasionally one or two ova are retained while the 
rest of the batch are deposited, and the presence of these retained ova 
is proof that the specimen has laid at least one batch of eggs. 

From laboratory experiments carried out at Amritsar in July, Chris- 
tophers found the rate of development to be as follows : — ■ 



CHOICE OF HOST 



263 



Twelve hours after hatching . . . Ovaries in first stage, salivar}' glands 

immature. 

Thirty-six hours after hatching. . . First appearance of yelk granules, 

ovary in second stage. 

Fourth day after hatching . . . Ovary in third stage, the nucleus 

obscured by yelk. 

Fifth day after hatching . . . Commencing elongation of follicle. 

Sixth day . . . Ovary in fifth stage, appearance of 

floats. 

Observations made on caught anophelines indicated that the rate 
of development of the second and succeeding batches of eggs is much 
more rapid than this, and that the second follicle, already at the second 
stage of development when the first batch of eggs is laid, is able to com- 
plete its growth in about two da5'S. 

The nature of the stimulus which induces mosquitoes to bite is not 

clearly understood. It is well known that mosquitoes, and particularly 

anophelines, are attracted to dark objects, and seem 

r , • , , , , , • , , '^'"''ce of Host 

to prefer to bite through a dark skm rather than a 

white one. In the Aden Hinterland, in the camp referred to above, 
the senior writer always found many more Anopheles in the tents of 
Indian soldiers than in those occupied b}- Europeans ; other observers 
have also noted the same peculiarity in the case of Anopheles in 
Africa. The reason for this choice of host is not very obvious, but it 
may be noted that the Indians were in the habit of keeping their tents 
almost completely closed, and the atmosphere in them was much more 
humid than in those occupied by the Europeans, who kept theirs 
partly open. 

Howletts' experiments tend to throw some light on this subject. 
This observer carried out a series of preliminarv experiments and found 
that shed blood or human sweat did not attract the females of Ciilex 
fatigans or Sfegoinyia sciitellaris any more than ^^■ater. On experi- 
menting with the effect of heat, however, it was at once found that the 
females of Stegomyia scitfellaris were readily attracted by the hot air 
radiating from a test tube containing hot water ; the male mosquitoes on 
the contrary paid no attention to it. As a result of a number of similar 
experiments he concludes that, ' (a) the bite of a mosquito is a reaction to 
' the stimulus provided hy a hot surface, {b) that the mosquito is attracted 
* to the hot surface mainly by the warm air rising from it, and (c) that the 
' strength of the reaction is, within certain limits, proportional to the 
' differential temperature " of the surface, i.e. the difference between its 



264 



MEDICAL ENTOMOLOGY 



' temperature and the general air-temperature at the time, and that this 
' difference must be positive '. 

With our present imperfect knowledge it is not possible to state what 
other influences may come into play in attracting mosquitoes to bite. 

Many interesting problems, some of them of considerable importance, 

might be stated with regard to the life history and bionomics of 

mosquitoes in general and the Anophelina in parti- 
Some Problems in 1 ^ ,• ■ i J 1 ,1 1, , 

Bionomics cular. One question is suggested by the well-known 

fact that female mosquitoes in captivity can be fed 

and kept alive for some time on a diet of banana, dates, or sugar water. 

What are the factors which govern their choice of food, and do they only 

occasionally, or habitually, feed on vegetable juices in addition to blood ? 

In some regions, as, for instance, certain parts of Greenland, mosquitoes 

are said to appear in swarms on the advent of a traveller, and to attack 

him, although previously the region was uninhabited and regular food, at 

least regular feeds of blood, apparently not available. Are such or any 

species capable of carr3'ing out their reproductive processes either on 

a purely vegetable diet or with the aid of the reserve food material 

carried over from the larval stage, while still retaining the faculty 

of obtaining and digesting vertebrate blood when the opportunity 

arises ? 

Perhaps the most interesting question, and the one with the most 
suggestive possibilities, is that of the choice of host from which mosqui- 
toes will suck blood. It is well known that certain species will feed on 
a variety of vertebrates, though it is by no means certain whether this 
is pure chance, or whether they are guided in their choice in some 
definite manner ; * in a considerable proportion of cases the blood parasites 
of mammals are peculiar to one species, and cannot thrive in the blood 
of another. If a mosquito, or any other blood-sucking arthropod for 
the matter of that, takes in from one host the infective stages of a parasite 
which can normally develop in its body, and at the next feed takes in 
blood from another host which does not harbour this particular species 
of parasite, will the blood of the second host affect the progress of the 
cycle of development of the parasite in its invertebrate host ? 

Many other questions will suggest themselves. The above will suf- 
fice to indicate the necessity for further enquiry. 

Most female mosquitoes may be induced to oviposit in captivity if 
their eggs are near maturit}'. When attempting to do this it is best 

* Possibly the difference in the normal temperature of different animals has some 
ijifluence in 4he choice of host. 



BREEDING TECHNIQUE: EGG LAYING 



265 



to keep only those females whose ovaries are seen as two white patches 

at the sides of the abdomen, an indication that the eggs are ready 

to be laid. Perry also points out that when a number 

of females are kept together they are much more likely Egg^iayitg^n'^Captu' 

to lay their eggs than if they are kept separately. It vity 

is true, however, that the females of some species 

whose eggs, at the time of capture, do not appear to be mature, will lay 

them if they are fed and kept long enough. 

The mosquitoes should be placed either in large test-tubes or wide- 
mouthed glass jars with screw tops. The method of using the tubes is 
as follows : — The tube — preferably a large one such as is used for cul- 
tivating bacteria on pieces of potato — should be thoroughly cleaned and 
dried, and a strip of cardboard firmly fixed in it. After the mosquitoes 
have been placed in it the mouth is covered with a piece of fine-meshed 
netting ; it is then inverted over some moist filter paper in a jar and 
placed in a dark cupboard. If the mosquitoes are wild ones an attempt 
should be made to feed them the second night after capture ; this is 
carried out by inverting the tube over the forearm. 

The best form of glass jar is the common jam or preserve bottle with 
a good screw top ; these can be purchased in most places at a small 
cost. The method of using such a jar was first devised by Christophers, 
and is as follows : — The jar is cleaned and dried, and a strip of cardboard 
is fixed diagonally across it ; it is then inverted over its own screw top, 
which should contain a very small quantity of water and several strips of 
filter paper. The mosquitoes, on being placed in the jar, will rest on the 
cardboard. They can be fed by placing the open end of the jar on the 
forearm ; this is accomplished by raising the jar from its lid until a piece 
of cardboard can be placed across the mouth ; when the jar is in position 
on the arm the card is withdrawn. In replacing the jar over the lid the 
cardboard is slipped under its mouth, which is then placed over the lid, and 
the cardboard gently withdrawn. The tubes and jars should be labelled 
and placed in a cupboard ; in cold weather they should be kept in an 
incubator which registers a temperature of about 75° F. The tubes and 
jars should be examined daily to see if any eggs have been laid on the 
filter paper ; all dead mosquitoes and soiled filter paper are removed and 
if necessary fresh water and paper added. It is best to lift the eggs off 
the filter paper with a moistened brush, and to place them on a fresh 
piece of moist paper in a dish containing a small quantity of water ; they 
may, however, be left on the paper in the screw top, care being taken to 
renew the water. 
34 



266 



MEDICAL ENTOMOLOGY 



The eggs of mosquitoes may be collected in the places in which they 
are laid by searching for them with a good hand lens. Those of the 
Anophelina will be found lying on any vegetable matter 
Collectin^g niosquito ^j^^ edge of water, either arranged irregularly or in 

characteristic star-shaped patterns ; their glistening 
appearance and the presence of floats render them easy of detection. It 
is often only necessary to collect some of the vegetable matter and to place 
it in a .large tray containing some water, and the larvae will appear in a 
few days. Small collections of water in tins and pots, in holes in 
rocks and trees are the kind of places where many Culicines lay their 
eggs, and it is important to remember that, as in the case of Stegomyia 
and its allies, the eggs may sink to the bottom of the receptacle or 
hole. In the case of small tins the water should be first stirred 
up and then poured into a white enamel tray ; as a rule the eggs 
are dark objects and can be readily recognized with the naked eye. 
In this way many eggs which adhere to the sides of the receptacle 
are washed out. Small collections of water in holes in trees and 
rocks are best removed by syphoning off the water after stirring it 
up ; if it is thought that any of the eggs are adhering to the sides 
of the hole fresh water may be added, and the process repeated 
until they have all been recovered. The well-known egg rafts of many 
Culicines are such large objects that they cannot escape detection ; they 
are best lifted out of the water with a brush. 

When the larvae hatch out of the eggs thus collected they should be 
transferred to specially constructed breeding trays or tanks. The 
important points connected with the rearing of mosquito larvae are 
dealt with below. 

Large numbers of mosquito larvae may be collected by dipping for 
them at the edges of streams, ponds, tanks and similar places. The 

simplest form of dipper, and one with which large num- 

Collecting Mosquito i ri i ij- u 4. 4.- 

, bers 01 larvae can be captured m a short time, is a 

Larvae ... 

shallow white basin, of which several sizes may be 

used. One side of the basin is lowered towards the surface of the water 
where the larvae are floating, and with a sudden movement its edge is 
passed under the water, which as it flows in carries the larvae with it. The 
water containing the larvae is then poured into a large bucket, and the 
dipping process repeated as often as is desired. Large spoons are also 
used for collecting larvae, but only a few can be caught with them at 
each dip. In large pools where there is a quantity of thick vegetation 
it is often difficult to locate the larvae, for they shelter themselves 



COLLECTING AND IDENTIFYING LARVAE 267 



among the stems and leaves of the water plants and can only be 
captured one at a time. In this case it is best to pull out most of 
the plants and, when the larvae have collected together after an interval, 
to dip for them in the usual way. 

Larvae may be collected from wells by using a simple and efficient form 
of apparatus devised by Bentley, the construction and use of which he 
describes as follows ; — ' A loop about fifteen to eighteen inches in diameter 
' is made of very thick brass or galvanized iron wire, and upon this frame 

* a shallow net of very thin mull-mull or muslin is stretched. The net is 

* suspended hy three short brass chains about two feet long, which are 
' attached to the frame below and to a small ring above. To the ring 

* a rope is tied, and the net can be lowered to any required depth. When 

* a well has to be examined the net is lowered to about a foot beneath the 
' surface of the water, the weight of the frame causing it to sink. It is 
' gently moved below the surface, and pulled up at a point some distance 
' from where it first entered the water. On examining the net, larvae, 
' if plentiful, are easily seen and can be secured by washing them off into 
' a bowl of clean water '. Bentley also recommends washing the net in 
a large-sized white enamel frying pan. 

In the laboratory the different kinds of larvae should be separated out, 
care being taken that predaceous species, such as those of Ciilex concolor, 
and dragon fly larvae, are removed to separate trays. 
The more important characters of taxonomic value, lapvae 
such as the structure of the antenna and syphon tube, 
the position of the palmate hairs and the number and structure of the 
leaflets, can be studied in the living larva ; for finer details it is best to 
make cleared preparations. With a little practice the worker will learn 
to recognize the larvae of the various species which are present in his 
neighbourhood. The several species of mosquito larvae which may be 
found breeding in the same collection are best identified by transferring 
them singly, with the aid either of a glass pipette or a small spoon, to a 
slide and placing a coverslip over them. In this way they are immobi- 
lized, though in no way damaged, and can be examined with a low power 
objective ; in the case of larger larvae it may be necessary to place them 
in a hollow glass slide. 

If a few imagines are required merely for purposes of identification 
larva may be kept in small trays, but it will soon be found that they 
do not thrive in these receptacles. It is difficult to obtain water 
containing suitable food and to keep it fresh. 

' In order to obtain the best results in rearing mosquito larvae they 



268 



MEDICAL ENTOMOLOGY 



should be placed in some form of breeding tank ; the trays used in the 

case of tabanid larvae (see Chapter 4, Section 2) will be found very 

useful for this purpose. The tray should be filled with 
Raising of imagines . r j ^ , . i < r i r 

from larvae ^ ^^'^^ ^ ^ depth of three or four 

inches, and the mud sloped off to simulate the edge of 
a pond ; fresh water is then poured into the tray until it is about three- 
quarters full. Some plants and grass should be dug out with their roots 
from the edge of a pond and planted in the mud ; not only do they 
afford excellent shelter for the larvae, but their stems and leaves har- 
bour animalculae and other forms of animal life suitable for food. 
The tray should be placed in front of a window or on a verandah with 
an eastern position, so that it receives direct sunlight for several hours 
in the morning. It may be necessary to cover the tray with a net in 
order to prevent stray mosquitoes from laying their eggs in the water ; 
this is accomplished by fixing stout wires to the sides of the tray, as is 
described in the case of the breeding of the Tabanidae. If large num- 
bers of adult mosquitoes are required for feeding experiments, larvae 
can be added to the tray daily, so that imagines will be available on 
each successive day. 

In the case of tabanid larvae, at least those of the larger species, little 
or no attention need be paid to the condition of the water in the tray ; 
although it may become stale, the larvae do not suffer much in con- 
sequence. With mosquito larvae, however, it is very different. After 
the water has been standing for several days a pellicle, consisting of 
flagellates, amoebae and bacteria, forms on the surface, and below this 
decomposition takes place. This has a most injurious effect on mosquito 
larvae, and if it is not attended to they cease to grow and eventually die. 
It is, therefore, important to aerate the water morning and evening, by 
forcing air through it ; a fine capillary tube and a rubber bulb, such 
as that attached to some form of syringe, may be used. Darling recom- 
mends the well-known Pacquelin cautery apparatus, which is used by 
attaching the double bulb to a glass tube with a capillary canal ; the air 
is forced through the glass into the water, which then remains fresh for 
a long time. 

When the larvae pupate, the pupae should be collected with a 
small spoon and transferred a small jar, which is three-quarters full 
of water. A similar jar, with a piece of cardboard fixed 
Methods of Iceeping inside it, is inverted over the mouth of the first ; both 
^qultoes """^ should be kept in a safe place. When the mosquitoes 
hatch out they fly into the upper jar and rest on the 



KEEPING AND FEEDING MOSQUITOES 269 



cardboard ; when all the imagines have hatched the upper jar should be 
removed and a piece of netting tied over its mouth. 

Darling recommends keeping mosquitoes in lantern chimneys, in the 
centre of which he fixes a circular piece of cardboard, securing the two 
ends with pieces of net ; about twenty mosquitoes are placed in each 
chimney, which should be placed in a jar with some moist filter paper 
and kept in a cupboard. 

Adie describes a simple method of keeping anophelines alive without 
feeding them on blood. In the jar he places a dried date wrapped in a 
small piece of muslin, a piece of wet sponge, and a twig of some green 
weed, the end of which is inserted into a hole in the sponge. If placed 
in a jar or lamp chimney under these conditions female anophelines may 
be kept alive for three weeks without blood. 

Caught mosquitoes can be induced to bite if certain precautions are 
attended to. The worker will, however, soon discover that many if not 
all of the bred females of certain species will refuse to suck blood ; no 
adequate explanation can be given for this, but it seems probable that 
copulation is in some way connected with the first feed of blood. 
Although female mosquitoes will readily suck the juice from a banana 
or a date, it has been shown that this food has no material effect on 
the development of the ova. It is clear, however, that a preliminary 
feed from a banana or a date will stimulate mosquitoes to bite later on. 

Feeding experiments should preferably be carried out in the evening, 
and at least twenty-four hours after the mosquitoes have hatched. 
The jar or the chimney should be inverted over the patient's forearm, and 
care should be taken to cover it with a dark cloth in order to 
exclude all light. A few taps on the bottom of the jar will cause the 
mosquitoes to alter their position, and if they are going to bite they 
will settle on the net and commence to feed at once ; in the case 
of the lamp chimney the same effect is produced by blowing through 
one end. After the mosquitoes have fed the jar is inverted over 
its lid, which should contain some moist filter paper. The chimneys 
should be placed upright in a jar, at the bottom of which there is 
some moist filter paper. 

If the mosquitoes refuse to bite an attempt should be made on 
the following night, and in the interval they should be given a date 
or raisin to feed on. If they still refuse to bite they should be 
liberated into a large cage covered a good net ; the bare arm should 
be passed inside the cage in the evening first moistening it with a 
little water. Sometimes even this method fails, and if this happens 



270 



MEDICAL ENTOMOLOGY 



the mosquitoes should be Hberated into a net fitted over a patient's 
bed. One of the writers found that this was the only way to feed 
Ciilex fatigans, which had been hatched from eggs, on Kala Azar 
patients. This last method of feeding mosquitoes is, however, seldom 
necessary. 

Mosquitoes can be fed on small birds, such as sparrows, canaries, 
owls, and pigeons, by liberating them in large cages containing the 
birds. Several strong wire supports should be fixed inside the cage 
for the birds to rest on. A muslin bag is secured over the head of 
the bird by tying it securely with two tapes under the wings ; this 
prevents it from flying about in the cage. 

In all feeding experiments with mosquitoes which have for their 
object the investigation of the life history of some protozoon it is 
imperative to use bred insects. It has already been 
Pitfalls in feeding pointed out that the early stages of certain flagellates of 
experiments rr , i ^ • r • 7- • i 

the genera Herpetononas and Crithidia occur in the 

alimentary tracts of mosquito larvae, so that breeding out the adults 
from larvae is not a certain means of excluding these parasites ; spirochaetes 
and certain microsporidia are also acquired by mosquitoes early in their 
larval stages. In the past these parasites have been a fruitful source of 
error, and there can be no doubt that they have been confused with 
blood parasites which the mosquitoes may ingest. The only way to 
exclude such parasites is to breed out the imagines from eggs, and to 
take the precaution of keeping the larvae in water which does not 
contain any encysted stages. The possibility of heriditary transmission 
should not be forgotten. 

The methods employed in dissecting mosquitoes will be dealt with at 
the end of Chapter IV. 



CHAPTER III 



SECTION 2 

THE ORDER DIPTERA : ORTHORRAPHA-BRACHYCERA 

The characteristic feature of this division of the Orthorrapha is the 
short type of antenna. Usually there are two or three simple joints, 
with or without a terminal arista, which in itself may consist of one or 
two joints with a terminal style. There is, however, a good deal of 
variation in the form of the antenna in the different families. In the 
Phoridae, for instance, the antenna consists of two or three simple joints, 
with a dorsally placed arista, thus approximating to the type seen in the 
Muscoidean flies, while in the Asilidae there are three joints and a 
terminal style. In the Tabanidae the antenna is specially modified and 
of an unusual shape. The wing venation is always more complex than 
that in the nematocerous flies ; a discal cell is always present, and the 
second long vein is never forked. 

Of the families contained in this division the Tabanidae are by far the 
most important, both because of their numerical preponderance and of 
the occurrence of the blood-sucking habit in so large a proportion of the 
species. In the Leptidae there are three or four species which are said 
to suck blood, but the habit is the exception rather than the rule in that 
family. The Asilidae, or ' robber flies ', are well known predaceous in- 
sects ; certain African species are said to attack man occasionally, though 
it is doubtful whether they do so with the intent to suck blood. 

FAMILY TABANIDAE 

Large, small, or medium -sized flies, with robust thick-set bodies and 
large heads, the surface of which is almost entirely occupied by the 
compound eyes. Antennae porrect and variable in structure, and always 
three-jointed ; the third joint is composed of from four to eight segments 
more or less distinctly separated from one another. In most of the genera 
the antennae are shorter than the head ; in Chrysops they are longer. 
The third joint often ends in a short or long blunt-pointed process. The 
eyes may be pubescent or bare, contiguous or nearly so in the male, with 
variously coloured bands in which the facets are large ; in the female the 



272 



MEDICAL ENTOMOLOGY 



eyes are separated by a broad white band, at the lowest border of which 
there are certain small dark longitudinal or transverse callosities or calli. 
Ocelli may be present or absent. Proboscis short or projecting down- 
wards, or long and projecting forwards. Palpi two-jointed, stout, of a 
pale creamy colour, as long as the proboscis or much shorter. Thorax 
broad, covered with fine hairs, never with bristles, and with or without 
stripes or other markings. Abdomen broad, composed of seven visible 
segments, and covered with delicate hairs, never with bristles; it may be 
marked with spots and bands. Male genitalia never prominent. Legs 
stout, tibiae sometimes dilated, middle tibia with two spurs at the tip, 
Empodium well developed, pidvilli always present. Venation character- 
istic and without much variation; two submarginal and five posterior 
cells present. The costal vein encircles the entire wing; the anterior 
branch of the third longitudinal vein often has a short backwardly 
directed spur. Wings often dark, with interrupted bands, clear flecks or 
rings. Squamae of large size. Reproduction oviparous, eggs laid in a 
mass on leaves or twigs over or near water. Larvae ichitish, cylindrical 
in shape and tapering at both ends ; they may be ringed or striped, and 
are provided with pseudopods and roxvs of small spines for locomotion. 
The pupa resembles that of Lepidoptera, but has large ear-shaped spir- 
acles on the dorsum of the thorax. 

This family is an extremely large one, no less than 2,500 species hav- 
ing been recorded up to the present time. It is widely distributed, 
and many of the species are common in favourable localities. The 
males throughout the family, and the females in many of the genera, 
are flower feeders or live upon vegetable juices. In some of the genera, 
such as Tabanus, Haematopota and Chrysops the females are blood- 
suckers, and the commoner species, which are brought to notice hy their 
habits, have received various local names, such as ' gad flies ', ' horse 
flies', 'clegs', ' seroot flies'. They feed mainly upon cattle and horses, 
but will occasionally attack man. The males of many of the species 
are very rarely met with, even in localities in which the females are 
quite common. 

Several observers have attempted to incriminate flies of this family as 
transmitting agents in certain trypanosome diseases of equines and 
camels, such as Surra and Debab, in India and North Africa. The 
evidence in the majority of instances is circumstantial, and is not 
borne out by transmission experiments. It is possible that the Taba- 
nidae may transmit the trypanosomes accidentally. (See Chapter XII.) 



FAMILY TABANIDAE : CLASSIFICATION 273 



Although it is generally easy enough to allocate a specimen of one 
of the' commoner genera, such as Tabantis, Haeinatopota, or Chrysops, to 
its proper genus, the identification of species in this 
family is often extremely difficult. The characters to *''^dentjf^p|^"Q^'"* 
be particularly noted are the size and shape of the 
frontal callus, and the character of its backward extension ; the shape 
and breadth of the front ; the structure and shape of the palpi and 
antennae, and especially of the terminal joint of the latter. Mere exami- 
nation of the antenna with a hand lens is apt to be misleading, as one 
frequently finds it very difficult to determine the exact number of the 
joints or rings, and their relative size, in this manner ; it is advisable to 
remove the part and to clear it in potash solution, and then to mount it in 
Canada balsam for examination under the microscope. The colouration 
and banding of the eyes, which is often extremely characteristic, especi- 
ally in the male, is not to be depended on as a taxonomic character, as 
it fades rapidly after the death of the insect. It should be noted in the 
fresh condition and recorded. 

Among the authorities on this family may be mentioned Austen, 
Griinberg, Newstead, Ricardo and Sourcouf, in Europe ; Hine and 
Williston in North America ; Lutz and Nieva in South America. Hine's 
papers on the life histories and breeding of the American species are of 
special practical value. 

The following key, to which some additions have been made, is taken 
from Miss Ricardo's papers : — 

FAMILY TABANIDAE 

A. Hind tibiae with spurs ; ocelli usually present . . . Subfamily 

Pangoninae. 

B. Hind tibiae without spurs ; ocelli absent . . • . Subfamily 



Tabaninae. 



A 

SUBFAMILY PANGONINAE 



1. Third joint of antenna with eight or at least seven segments ; 



proboscis usually prolonged ......... 2 

Third joint of antenna with five segments ; proboscis short . Silvius, etc. 12 

2. Third joint of antenna with a tooth Oicrania. 

Third joint of antenna without a tooth ........ 3 

3. Wings short ; body short and elliptical ..... Apocampta. 
Wings short ............. 4 

35 



274 



MEDICAL ENTOMOLOGY 



4. Third joint of antenna with each segment branched . . . Pityocera. 
Third joint of antenna not branched 5 

5. Upper corner of eyes terminating in an acute angle . . . Qoniops. 

Upper corner of eyes not terminating in an acute angle ..... 6 
5. Antenna deep-seated, inclined downwards ; palp very large 

and thick Cadicera. 

Antenna not deep seated not inclined downwards ; palp not 

very large and thick ........... 7 

7. Antenna subulated ; proboscis with terminal lips in form of a 

hatchet ; anal cell open and anal vein curved . . Pelecorhynchus. 

Antenna not subulated; proboscis simple; anal cell closed, 

anal vein not curved ........... 8 

8. Proboscis scarcely extending beyond palpi .... Apatolestes. 
Proboscis extending beyond palpi ......... 9 

9. Wing with fourth posterior cell closed ........ 10 

Wing with fourth posterior cell open ........ 1 1 

10. Eyes not bare .......... Scione. 

Eyes bare Dorcalaetnus. 

11. Wing with first posterior cell ctosed ; eyes bare or hairy . . Pangonia. 

(including subgenera) Erephrosis and 
5ubpangonia.) 

Wing with first posterior cell open ; eyes hairy or bare . Diatomineura. 

(including subgenus) Corizoneura. 

SILVIUS AND ALLIED GENERA 

12. First and second joints of antenna short ........ 13 

First and second joints of antenna long . . . . . . . .18 

13. First joint of palp thickened ....... Scepsis. 

First joint of palp not thickened ...... Adersia. 

14. Second segment of abdomen unusually large; spurs on tibiae 

small Pronopes. 

Second segment of abdomen not unusually large ; spurs on 

tibiae not unusually small . . . .15 

15. Face concave in the middle ....... Rhlnomyza. 

Face not concave in the middle . . . . . . . . .16 

16. Wings with first posterior cell open ..... Silvius. 

(including subgenus Esenbeckia.) 

Wings with first posterior cell closed ; frontal callus absent . Aegophagamyia. 

Wings with first posterior cell closed ; frontal callus present. Bouvierella. 

17. Third joint of antenna with an acute spine on the first annulation Qastrixodes. 
Third joint of antenna with no spine on the first annulation, . . . 18 

18. Second joint of antenna as long, or nearly as long, as the first 

joint ; wings usually with black or brown designs . . Chrysops. 



B 

SUBFAMILY TABANINAE 

1. Third joint of antenna consisting of four di\'isions, without a 

tooth or angulation ........... 2 

Third joint of antenna with five divisions 5 



FAMILY TABANIDAE : SUBFAMILY TABANINAE 275 

2. Rings of the third antennal joint so distinctly divided that the 

antenna appears as if six-jointed ...... Hexatoma. 

Rings of third antennal joint not so distinctly divided ; the 

antenna always appears as if three jointed ....... 3 

3. Wings marked with rings and circles of darker colouring . Haematopota. 
Wings not so marked ........... 4 

Wings dark with light markings, but without the characteristic 

streaks of Hacmafopota Hippocentrum. 

4. First and second antennal joint in the male pubescent ; third 

joint longer than the first. Eyes hairy .... Dasybasis. 

5. First antennal joint globular situated on a protuberant pro- 

jection of the forehead Boldodimyia. 

First joint of antenna not globular ......... 6 

6. Third joint of antenna simple, not furnished with a tooth or 

angular projection ........... 7 

Third joint of antenna furnished with a tooth or distinct 

angular projection ........... 9 

7. Body covered with metallic scales Lepidoselaga. 

Body metallic in colouring 5elasoma. 
Body without metallic scales or colouring ; the first antennal 

joint longer than is usual in Tabanus ; wings usually with 

brown markings ............ 8 

8. Antenna long, the third joint cylindrical and situated on a 

projecting tubercle ........ Udenocera. 

Antenna short, Tabanus-\ike, situated on a prominent 

tubercle Neotabanus. 

Antenna not very long, the third joint not cylindrical, and not 

situated on a projecting tubercle ...... Diachlorus. 

9. Abdomen short, stout and very convex ..... Stibasoma. 
Abdomen neither short, stout or convex . . . . . . . 10 

10. Antenna long and slender, the first joint long . . Acanthocera. 
Antenna neither long or slender, nor is the first joint long . . . . 11 

11. Species of a slender build, usually with a banded thorax and 

abdomen ; third joint of antenna slender, mostly with brown 

markings on wings ........ Dichelacera. 

Species of a stouter build ; third joint of antenna stout , . Tabanus. (sens, lat.) 

In the above key three Ethiopian genera, Thaumastocera, Holoceria 
and Parahaematopota, recently erected by Griinberg, have been omit- 
ted, as each contains only one species. According to Griinberg the genus 
Thaumastocera (T. akwa, Griin.) is separ-ated from the South Ameri- 
can genus Stibasoma by the curiously shaped third segment of the 
antenna, which has two deep notches in its superior margin in the 
female ; in both sexes the angle at the base ( superior ) is extended into 
a process which extends as far as the end of the joint. Holoceria {H. 
nobilis, Griin.) and Parhaematopota are closely allied to Haematopota, 
and are considered by Austen to be of doubtful validity. H. nobilis has 
the general facies of a Haematopota, but is without the characteristic 
streaks and circles of white on the wings. The thorax is dark, with two 



274 



MEDICAL ENTOMOLOGY 



admedian dark bands ; abdomen of a steely grey. According to Neave 
it is widely distributed in the wooded parts of eastern tropical Africa. 

Hine gives the following Key to the North American genera of 
Tabanidae : — 

1. Hind tibiae with spurs at the tip ......... 2 

Hind tibiae without spurs .......... 6 

2. Third segment of the antenna composed of eight annuU the first 

of which is only a httle longer than the following ones .... 3 
Third segment of the antenna composed of only five annuli 
the first of which is much longer than the following ones ; 

ocelli present ............ 5 

3. Front of male narrow ; ocelli present or absent ; fourth pos- 

terior cell at least open ....... Pangonia. 

(Diatomineura, Corizoneura.) 
Front of female broad with a denuded callus ; ocelli present .... 4 

4. Eyes in the female acutely angulated above ; wing in both 

sexes with a dark picture ....... Qoniops. 

Eyes in the female not acutely angulated above ; wings 

hyaline. Apatolestes. 

5. Second segment of the antenna about half as long as the first ; 

eyes in life with numerous small dots ..... Silvius. 
Second segment of the antenna as long or but little shorter 

than the first ; wing with a dark picture .... Chrysops. 

6. Third segment of the antenna with a well developed basal 

process . Tabanu5. 

(Therioplectes. Atylotus.) 
Third segment of the antenna without, or with a rudimentary 

basal process ............ 7 

7. All the tibiae enlarged, the hind pair ciliate .... Snowiellus. 
None of the tibiae enlarged and the hind pair not ciliate. .... 8 

8. Front of the female as broad as long ; the callus transverse . Hematopota. 
Front of the female narrow ....... Diachlorus. 

GENUS TABANUS, L. 

Small to very large thick-set insects. The head is as a rule broader 
than it is high; the eyes may be nude or hairy. In the male the eyes 
have irridescent bands, in xvhich the facets are larger than in the rest of 
the surface. The colours of these bands fade rapidly on the death of the 
insect. In the female there are no irridescent bands and the colouration 
is usually uniform ; in some species the females have brightly coloured 
bands, in which case the eyes of the male are similarly marked on the 
lower surface. In a few species (subgenus Therioplectes, Zeller ) the eyes 
are pubescent, but the hairs as a rule are not very apparent. Ocelli are 
always absent, but there may be a small tubercle on the vertex (Therio- 
plectes) ; it is absent in the subgenus Atylotus. The eyes of the female 
are widely separated; situated on the forehead between them there are 



ORIENTAL SPECIES OF TABANUS 



277 



usually one or two small raised knobs or bands of a dark colour, the 
calli ; the lower of these may be transverse or broadened transversely, the 
upper round or oblong ; in the majority of species one of these is produced 
upwards to the vertex as a narrotc line; rarely both are so produced. 
One or both of the calli may be absent. The antennae are three-jointed 
and are shorter than the head ; the proximal joint is short, the second 
very short, only about one-third as long as the first, the distal joint as 
long as the first and second together. The third joint is stylifonn, 
consisting of four segments, and has a dorsal spine or hook at its basal 
end. The thorax is broad, and often has longitudinal stripes. The 
abdomen is slightly broader than the thorax, and may be banded with 
stripes or only marked with spots. The wings are large, and usually 
clear, but there may be spots and bands. The anterior branch of the 
third longitudinal vein may or may not have a backwardly directed spur. 

Miss Ricardo gives the following table of the Oriental species of 
Tabanus : — 

•Table -OF Groups 

J _ Eyes bare ............. J J 

Eyes hairy (Therioplcctes) ....... Group XI 

II, Forehead with two separate caUi, the first one usually 
transverse, the second irregular in shape, smaller. Fore- 
head four to six times as long as it is broad. Small 

species 9 to 14 mm. in length . . . - HI 

III. Thorax and scutellum same colour. Abdomen with no 

bands , Group I 

Scutellum white or yellow-haired. Abdomen with white 
or yellow-haired bands ....... Group 1 1 

IV. Forehead with two small round spot-like calli, one above 

the other, never united ...... Group m 

V, Forehead with no callus ....... Group ly 

VI. Forehead with one square, narrow, or oblong callus, which 
is always prolonged towards the vertex by a more or less 
narrow line 

VII. Wings with spots or bands Group V 

Wings distinctly marked with brown or yellow colouring, 
but not in the form of bands. Large species 18 to 23 mm. 

in length Gkoup VI 

Species with one or more stripes, usually continuous, on 
abdomen. Forehead five to nine times as long as it is 

broad . Group VII 

Species with median or lateral spots or both on abdomen, 
not usually forming a continuous stripe. Forehead four 
to ten times as long as it is broad Group VIII 



VII 



278 



MEDICAL ENTOMOLOGY 



Species with paler bands and sometimes spots on abdomen. 

Forehead four to ten times as long as it is broad . . Group JX 
Species with abdomen unicolorous or almost so, sometimes 

darker at apex. Forehead five to ten times as long as it 

is broad Group X 

vin. Species with eyes pubescent and an ocelligerous tubercle 

on forehead at vertex ...... . Group XI 



Table of Species 

Group I. 

1. Subcallus shining. Eyes witii no cross-bands. ...... 2 

Subcallus not shining. Eyes with cross-bands ...... 3 

2. P'rontal callus reaching eyes. Abdomen grey, covered, with 

long white pubescence. Tibiae whitish, with long fringes of 

white hairs rarus. 

(Federated Malay States.) 
Frontal callus not reaching eyes. Abdomen black, shining. 

Tibiae whitish, but with no long fringes of white , , hirtipalpis. 

(Nepal.) 

3. Frontal callus reaching eyes. Black species with three grey 

stripes on abdomen bicallosus. 

(Pusa, Bengal ; Madras.) 

Group II. 

4. Dark brown or yellowish-brown species with yellow-haired 

scutellum and yellow-haired bands on abdomen ..... S 

Black species with white-haired scutellum and white-haired 

bands on abdomen 6 

5. Abdomen reddish brown or yellow with six narrow yellow 

bands. Palpi pale yellow with black and yellow pubescence. 

Fore tibiae pale on basal two-thirds only .... flavicinctus. 

(Assam; South India.) 

Abdomen dark reddish-brown or blackish with two broad 
yellow bands. Palpi black with grey tomentum, and white 
and black hairs. Fore tibiae pale to apices . . leucocnematus. 

(Assam, Burma.) 

6. Abdomen black with two white bands. Frontal callus almost 

reaching eyes. Fore tibiae pale on basal two-thirds only. 

Wings tinged brown on fore border . • . . , bicinctus. 

(South India ; F. Malay States.) 
Abdomen with six white bands. Frontal callus not reaching 
eyes. Fore tibiae pale to apices. Wings clear . . . sexcinctus. 



(Burma.) 



Group III. 

7. Forehead slightly narrower anteriorly, three and a half to 

four times as long as it is broad ........ 

8. Abdomen blackish covered with golden yellow tomentum and 

appressed yellow pubescence ...... fulvus. 



(China.) 



ORIENTAL SPECIES OF TABAUNS 



279 



Abdomen yellowish with median and lateral blackish or brown- 
ish stripes ditaeniatus. 

(Africa to India ; China and Japan ; common in South India.) 

Group IV. 

9. Abdomen brown, reddish at base, covered with grey tomentum 
and with two small roimd greyish spots on the segments. 
Wings with no appendix. Length 7J to 11 mm . . . virgO. 

(Bengal ; South India.) 
Abdomen blackish brown with median and lateral greyish 

tomentose spots. Wings with an appendi.x. Length 13 mm. nemocallostis. 

(Bengal.) 

Abdomen covered with greyish-yellow tomentum and with 
thick short yellow pubescence in female ; abdomen of male 
the same but a black median stripe often appears. Wings 
with no appendix. Length 11| to 12J mm. negativus. 

(Formosa ; China.) 

Group V. 

10. Wings with four dark spots. Abdomen reddish brown, with 

white spots javanus. 

(Java.) 

Wings with one cross-band, the first posterior cell open . . . . 11 
Wings with two cross-bands, the first posterior cell closed or 

very narrow . . . . . ..12 

11. Forehead narrowest at vertex. Abdomen reddish, darker at 

apex, with small white median spots ..... optatus. 

(Bengal ; Borneo ; Sumatra.) 
Forehead narrowest anteriorly. Abdomen yellowish, darker 

at apex with larger white spots ...... non-optatus. 

(Bengal.) 

12. Abdomen brownish yellow, with broad yellow posterior bands 

on each segment, under side yellowish. Antennae reddish 

yellow. Male with equal facets to eyes .... flexilis. 

(Celebes.) 

Abdomen brownish red with narrower yellow bands, under 
side darker. Antennae reddish yellow, black at apex. 

Male with unequal facets to eyes vanderwulpi. 

(Philippines.) 

Group VI. 

13. Wings dark rich brown, the disal cell clear. Large black species 
with orange red pubescence on face and breast. Antennae 

red pratti. 

(Malacca ; Sarawak ; Selangor.) 
Smaller species similar in colouring. Antennae black . fuscicornis. 

(Formosa.) 

Wings yellowish or brownish, very distinctly tinged with 
. brown at apex and on posterior border. Scutellum yellow 

or greyish ............. 14 

14. First posterior cell of wings closed or very narrow . . . . . . 15 

First posterior cell open, not very narrow • 16 



280 



MEDICAL ENTOMOLOGY 



15. Abdomen reddish brown, narrow, with grey tomentose bands 

and median spots. Palpi slender. First posterior cell 

closed nephodes. 

(Assam.) 

Abdomen brown with narrow grey tomentose bands but no 
median spots. Palpi, large, broad. The first posterior cell 

very narrow at border albof asciatus. 

(Assam.) 

Abdomen black, livid at base. Smaller species. First pos- 
terior cell closed ........ basalis. 

(Sumatra.) 

16. Large yellowish species with blackish bands on the abdomen . aurifiamma. 

(Sylhet, Assam.) 

Group Vn. 

17. First posterior cell closed. Yellowish species with indistinct 

median black stripe on abdomen ...... annamitus. 

(Male) (Cochin China.) 

First posterior cell open .......... 18 

IS. Frontal callus oblong or narrow with lineal extension. 

Forehead at least five times as long as it is broad 19 

Frontal callus large, somewhat protuberant, almost square, 
with short lineal extension. Forehead three or four times 

as long as it is broad ........... 36 

19. Abdomen with a median stripe and lateral stripes or spots . . . , 20 
Abdomen with one median continuous stripe only, no lateral 

spots, or only isolated ones on the second segment ..... 27 
Abdomen with lateral stripes only ......... 35 

20. Frontal callus with a spindle-shaped lineal extension . . . . . 21 
Frontal callus with the lineal extension not spindle-shaped .... 22 

21. Abdomen blackish or reddish brown with grey median and 

lateral stripes, almost all the same length .... striatum. 

(Widely distributed 

throughout India ; Burma ; Assam ; Ceylon ; Malay ; Sumatra ; Java and Philip- 
pine Islands.) 

Abdomen with grey median stripe beginning only on the third 
segment, and with lateral stripes ending on the third or 
fourth segment . . . . . . hilaris. 

(Bengal ; Assam ; S. India.) 

22. Abdomen with a median stripe, the side spots small and 

indistinct ............. 23 

Abdomen with a median stripe, the side spots large and 

distinct. ............. 24 

23. Smaller species. Abdomen reddish yellow, darker at apex. 

Thorax blackish. Forehead eight times as long as it is 

broad abbreviatus. 

(Bengal ; Java ; Formosa.) 

24. The median abdominal stripe composed of almost equal sized 

spots not very large ........... 25 

The median abdominal stripe composed of spots of [unequal 
size, those on the third and fourth segments very large 

and conspicuous . . . . . . . . . , . , 26 



ORIENTAL SPECIES OF TABANUS 



281 



25. Abdomen and thorax lilac or blackish brown, femora blackish. 

Forehead about five times as long as it broad . . rubidus. 

(Bengal ; Bombay ; 

Assam ; South India ; Malay Peninsula ; Java ; Sumatra ; closely allied to autum- 

nalis and albimedius. 

Abdomen and thorax obscurely reddish brown, femora reddish 

brown. Forehead five to six times as long as it is broad . albimedius. 

(Widely distributed in India ; Nepal to Ceylon ; Bombay to Bengal.) 

26. Abdomen and thorax reddish brown, femora blackish. Fore- 

head about seven times as long as it is broad . . . speciosus. 

(South India ; Ceylon.) 

27. Median stripe of abdomen grey tomentose, or white or yellow- 

haired ............. 28 

Median stripe of abdomen black . . . . . . . . .31 

Median stripe of abdomen golden haired 32 

28. Forehead barely half as wide anteriorly as it is at vertex. .... 29 
Forehead parallel or nearly so ......... 30 

29. Small brown species. Femora brownish. Wings clear, brown 

on fore border hirtistriatus. 

(Federated Malay States.) 

30. Large black or reddish brown species, median abdominal 

stripe narrow. Femora black. Wings tinged brown . monotaeniatus. 

(Assam.) 

Brown species, the median abdominal stripe broad, the two 
round spots on second segment. Femora reddish wings 

brown on fore border brunnipennis. 

(Siam ; United Provinces ; India.) 

31. Abdomen reddish, black at apex, a narrow grey stripe often 

apparent on the median black stripe ..... abscondens. 

(Burma.) 

32. Forehead parallel ............ 33 

Forehead narrower anteriorly . . . . . . . . . .34 

33. Abdomen yellowish brown, darker at apex, the median stripe 

a dull, golden hair indistinct auristriatus. • 

(Canara, India) 

34. Abdomen yellowish brown or dark brown, the median stripe 

broad. Fore femora yellowish. Wings brown, especially on 

fore border hybridus. 

(Assam ; Malay ; Sarawak ; Borneo ; South China.) 
Abdomen covered with yellowish tomentum, median stripe 

very broad. Fore femora black. Wings clear . aurotestaceus. 

(China.) 

35. Black species. Abdomen with ferruginous lateral stripes on 

the first four segments. Legs blackish brown . . tristus. 

(Sumatra.) 

36. Forehead narrowest anteriorly ......... 37 

Forehead narrowest at vertex .......... 38 

37. Small black species. Abdomen with a median grey stripe 

beginning on the third segment only, the lateral stripes 

terminate on the second segment ..... jucundus. 

(Punjab; N.-W. Provinces; Bombay; Ceylon; China.) 

38. Small brown species. Abdomen with a median grey stripe , puteus. 

(Ceylon.) 

36 



282 



MEDICAL ENTOMOLOGY 



Group VIIL 

39, Wings with first posterior cell closed or at least very much 
narrower at border. Forehead six to seven times as long as 
it is broad .......... 

Wings with first posterior cell open, never very narrow at 
border .......... 



40. 



41. 



42. 



43. 



44. 



45. 



40 



41 



Abdomen with three series of grey spots on abdomen, reddish 

brown in male, blackish in female ..... amaenus. 

(China; Formosa; Japan.) 

Abdomen with three grey spots on the first two or three 

segments only, a larger, broader bodied, blackish species . mandarinus. 

(China ; Formosa ; Japan.) 

Forehead narrow, six to ten times as long as it is wide 

anteriorly, with a long narrow frontal callus ..... 

Forehead broader, four to five times as long as it is wide 
anteriorly, with a larger nearly square, or pear-shaped 
frontal callus ........... 

Brown, reddish brown, or reddish yellow, medium sized or 
large species, the triangular greyish or yellowish spots not 
usually forming a continuous stripe ....... 

Large unicolourous reddish species with small median indis- 
tinct white spots ........... 

Reddish brown or brown species with large prominent median 

whitish spots on the third and fourth segments only .... 

Reddish species with black spots ........ 

Small species with a narrow yellow abdomen irregularly 
marked with black and with three series irregular shaped 
grey median and lateral spots varicolor. 



42 



52 



43 

49 

50 
51 



(Borneo.) 



Medium sized species, 17 to 18 mm. in length. Abdomen 
reddish yellow with small median white spots. Forehead 
almost parallel or barely a third narrower anteriorly, six 
times as long as it is broad. Frontal callus oblong, not 
reaching the eyes. Wings clear, faintly tinged yellowish 
brown ........... 

Large brown or reddish brown species usually 18 to 25 mm. in 
length with abdominal median spots. Forehead from one- 
third to half narrower anteriorly, frontal callus long and 
narrow .......... 

Forehead eight to nine times as long as it is broad, about 
one-third narrower anteriorly ...... 

Forehead very narrow, eight to ten times as long as it is 
broad, only half as wide anteriorly as at vertex . 

Abdomen reddish, or reddish yellow, large, broad, with 
median short triangular yellow spots often indistinct. Fore 
tibiae reddish yellow on basal half, with black pubescence. 
Wings large, tinged yellowish brown or almost clear. Fore- 
head almost parallel ........ 



rubicundus. 

(Assam. 



44 
45 
46 



stantoni. 



(Malay.) 



ORIENTAL SPECIES OF TABANUS 



283 



46. 



47. 



48. 



49. 



50. 



51. 



indianus. 



Abdomen reddish brown, long, narrow, with median long 

triangular, distinct whitish spots, usually joining each other. 

Fore tibiae white on basal half with white pubescence. 

Wings long, faintly tinged yellowish brown. Forehead 

about a third narrower anteriorly ..... 

(Canara, S-W. India ; Formosa.) 
Abdomen blackish brown with almost hemispherical white 

medium spots. Fore tibiae blackish. Legs and palpi 

blackish. Wings clear, tinged brown. Forehead about a 

third narrower anteriorly ...... 



brunneus. 



Forehead eight times longer than it is broad, the frontal callus 
not reaching eyes ........ 

Forehead ten times as long as it is broad, the frontal callus 
reaching eyes ......... 

xVbdomen dark reddish brown or reddish yellow, with indis- 
tinct small greyish or yellow-haired median spots often 
absent. Thorax blackish with some yellowish grey tomen- 
tum. Fore tibiae pale on basal half. Wings slightly 
tinged with brown. Male with unequal facets on eyes 

(Malay 

Smaller species. Abdomen reddish brown with distinct bright 
yellow haired median spots, and similar lateral spots on the 
second to fifth segments. Thorax blackish with greyish 
yellow tomentum ........ 

Larger species. Abdomen broad, reddish brown with indis- 
tinct median spots and some lighter segmentations. Thorax 
reddish with some grey tomentum. Wings nearly clear. 
Fore tibiae pale on basal two-thirds. Male with equal 
facets to eyes ......... 



(Java.) 
47 
48 



fumifer. 

; Sumatra : 



Borneo. 



malayehsis. 

(Malay.) 



factiosus. 

(Celebes; Philippines.) 



Abdomen reddish brown, median spots indistinct, small whitish. 
Thorax reddish, thickly covered with ashy grey tomentum. 
Wings clear dissimilis. 



Abdomen and thorax reddish, shining, nearly devoid of pube- 
scence. Wings clear. Palpi ending in an acute point . ignobilis 

Abdomen and thorax reddish, Wings tinged yellowish brown, 

Palpi ending in an obtuse point ...... nexU5 



(Borneo. 



(Borneo. 



Red-brown species with the large median white spots on third 
and fourth segments of abdomen, and white spots on the 
lateral borders of first four segments. Tibiae reddish 
(Male) signifer. 



(Borneo.) 



(China, 
significant 



Brown species with the same median spots, but with lateral 
white spots on the first two segments only. Tibiae-white . 

(India; Federated Malay States.) 
Abdomen reddish, the apex dull black with large black median 

spots on the second and third segments . . . _ . fuscomactilatus 

(Burma ; Sikhim.) 



284 



MEDICAL ENTOMOLOGY 



52. Frontal callus square. Small black species with white haired 

median abdominal spots, Legs blackish, tibiae yellowish . leucopogon. 

(India; Sikhim.) 

Frontal callus pear-shaped. Large reddish brown species, 

abdomen with median triangular spots. Legs reddish brown discrepans. 

(Ceylon.) 

Group IX. 

53. First posterior cell closed . . . . . . . . . . .54 

First posterior cell not closed . . . . . . . . .55 

54. Large blackish species with narrow fulvous bands on abdomen servillei. 

(Java.) 

55. Abdomen blackish brown, the first two segments covered with 

grey tomentum (Male) ........ crassus. 

(Canara, India ; Java.) 

56. Forehead narrow, seven or eight times as long as it is broad, 

frontal callus narrow with a lineal extension. Black or 

brown species ............ 57 

Forehead broader, four or five times as long as it is broad, 
frontal callus large with a stout, broad, or spindle-shaped 

extension ........ ..... 62 

57. Large black or brown species 21 mm. in length, with very 

narrow pale bands on abdomen ......... 58 

Smaller blackish species, 15 to 17 mm. in length, with 

whitish bands on abdomen .......... 59 

58. Brown species. Scutellum and sides of thorax with pale to- 

mentum. Legs blackish, tibiae obscurely reddish . . alboscutatus. 

(India.) 

Black species. Scutellum and sides with no such pale 

tomentum. Legs black, tibiae yellowish white . . . explicatus. 

(Sikhim ; Assam ; India.) 

59. Forehead narrower anteriorly. ......... 60 

Forehead hardly narrower anteriorly, but parallel . . . . . 61 

60. Frontal callus large, reaching the eyes. Antenna, legs, and 

palpi wholly black. Wings clear or tinged smoky brown nicobarensis. 

(Nicobar Islands.) 

Frontal callus narrow. Antennae and legs blackish. Palpi 

yellow. Wings brownish . . . . . . .. justorius. 

(Borneo.) 

61. Frontal callus narrow, not reaching eyes. Antennae and legs 

black. Palpi black, paler on insides. Wings faintly tinged 

brown khasiensis. 

(Assam, Meerut, India.) 

62. Brown or black species with whitish bands and spots on abdo- 

men .............. 63 

Reddish yellow species with whitish bands and spots on abdo- 
men .............. 64 

63. Abdomen reddish brown or blackish brown with broad white 

bands and large triangular median spots. Palpi short and 

stout sanguineus. 

(Bengal ; Assam ; Malay'Peninsula ; Java ; China.) 



ORIENTAL SPECIES OF TABANUS 



285 



Smaller species. Abdomen black with narrow white-haired 
segmentations and smaller - triangular spots. Palpi slender oxyceratus. 

(Himalayas ; China Hills ; Burma.) 



64. Abdomen reddish yellow, darker at apex, with narrower yellow- 

ish white segmentations, and median spots. Legs black, 

tibiae yellowish . . . orientis. 

(North India, Nepal, Bhutan.) 
Abdomen similar, but the last four segments are black . fulvimedius. 

(Nepal and Chin Hills; Burma.) 
Smaller species. Abdomen similar to that of orientis 

Legs wholly yellow consanguineus. 

(Malabar, India.) 

Group X. 

65. Black or brown species. Forehead narrower anteriorly, seven 

to ten times as long as it is broad. ........ 66 

Large reddish yellow species from 20 to 24 mm. in length. 

Forehead six to ten times as long as it is broad ...... 72 

Dark reddish species from 18 to 22 mm. in length. Forehead 

seven to ten times as long as it is broad ....... 75 

Reddish or reddish yellow species from 16 to 19 mm. in length. 

Forehead six to ten times as long as it is broad ...... 76 

Smallspecies reddish, yellowish, brownish, or blackish, from 

12 to 16 mm. in length. Forehead five to ten times as long 

as it is broad ............ 79 

66. Thorax paler than abdomen with yellowish tomentum and 

pubescence ............. 67 

Thorax not paler than abdomen ......... 68 

67. Dark brown or blackish species with yellowish brown thorax. 

Legs black, tibiae white. Wings tinged yellowish brown . birmanicus. 

(Burma ; Malay.) 

Reddish brown species with light yellow or greyish thorax. 
Legs black, tibiae white, middle and posterior femora yel- 
lowish. Wings brownish, clear at apex ... . fiavothorax. 

(Malay,) 

68. Wings yellowish brown, yellow on fore border. Black species. 

Thorax with short red pubescence ..... tinctothorax. 

(Malay ) 

Wings brownish or black. Brown or Clack Species ..... 69 

69. First posterior cell of wing closed. Abdomen deep black. . nigrotectus. 

(Siam.) 

First posterior cell of Wing not closed ........ 70 

70. Blue-black species. Thorax red at base. Antennae reddish 

brown. Posterior tibia red at base ..... caerulescens. 

(Java.) 



Forehead almost parallel. Abdomen dull reddish brown with 
greyish blue tomentum. Antennae reddish yellow, black 
at apex. Tibiae dull red or blackish. Beard and palpi black, tenebrosus. 

(Canara, India; Celebes.) 

Forehead narrower, not parallel . . . . . . . . .71 

71. Abdomen blackish. Antennae reddish yellow. Tibiae dull 

reddish. Beard white and black. Palpi yellowish . . parakinsis. 

(Malay,) 



286 



MEDICAL ENTOMOLOGY 



Abdomen dull blackish, conical. Antennae black. Tibiae 

black. Beard and palpi black inobservatus. 

(Sumatra.) 

72. Forehead parallel, six times as long as it is broad ...... 73 

Forehead narrower anteriorly, eight to ten times as long as it 

is broad. ............. 74 

73. Broad-bodied reddish-yellow species. Antennae yellow. 

Legs reddish brown ........ fulvissimus. 

(Borneo ; Sumatra.) 

74. Thorax brownish. Antennae reddish, the third joint black. 

- Femora i-eddish brown. ....... univentris. 

(Borneo.) 

Thorax yellowish. Antennae, palpi and legs yellow. . . flavissimus. 

(Ceylon.) 

75. Abdomen reddish brown, covered posteriorly with yellowish 

brown tomentum, and yellowish pubescence. Forehead 

seven times as long as it is broad. Beard white. . pauper. 

(Sarawak.) 

Abdomen dull reddish brown with black pubescence. Fore- 
head seven times as long as it is broad. Beard brownish, 
scanty. Fore coxae with white hairs ..... leucohirtu5. 

(Canara, Bombay.) 

Abdomen dull reddish brown with black pubescence. Fore- 
head ten times as long as it is broad. Beard brown, thick. 
Fore coxae with black hairs. ...... atrohirtus. 

(Ceylon.) 

76. Forehead ten times as long as it is broad. Frontal callus long 

and narrow. Abdomen reddish yellow, darker at apex. 

Legs black, tibiae whitish at base. ..... pallidepectoratus. 

(Assam ; Cochin China.) 

Forehead six to seven times as long as it is broad ..... 77 

77. Forehead narrowest at the vertex, abdomen reddish. Legs 

wholly red nigropictus. 

(India.) 

Forehead narrowest anteriorly ......... 78 

78. Abdomen narrow, reddish brown, under side with bands. 

Thorax reddish. Legs black, tibiae white at base . . joidus. 

(Assam.) 

Abdomen conical, reddish yellow, the apex black, underside 
the same. Thorax blackish. Legs black, fore tibiae dull 
reddish yellow on basal half, others wholly so . . siamensis, 

(Siam.) 

79. Forehead five times as long as it is broad, narrower anteriorly. 

Frontal callus club-shaped. Small reddish brown species. 

Palpi slender, hairy. ........ palpalis. 

(India.) 

Forehead five to six times as long as it is broad, parallel, or 

nearly so. Frontal callus oblong or club-shaped .... 80 

Forehead seven to ten times as long as it is broad, narrower 

anteriorly. Frontal callus long and narrow or oblong .... 83 



80. Yellow species. Thorax and scutellum covered with grey 
tomentum and yellow pubescence. Legs and antennae 



ORIENTAL SPECIES OF TABANUS 



287 



yellow. Palpi stout, ending in a long fine point. Frontal 

callus yellowish, often indistinct flaviventris. 

(Bengal ; Assam ; Ceylon.) 
Reddish brown species. Frontal callus reddish brown, always 

distinct ............. 8 1 

81. Thorax and scutellum blackish. Palpi slender, long. Anten- 

nae black at tip. Legs black, tibiae reddish yellow . . diversifrons. 

(Bengal ; Sylhet, Assam.) 
Thorax and scutellum usually reddish. Palpi stouter. 

Antennae not black at tip . . . . . . . . .82 

82. Abdomen reddish brown, unicolourous. Legs reddish yellow, 

femora often darker subcinerascens. 

(Burma.) 

Abdomen marked with grey tomentum, giving it the appear- 
ance of having zigzag indistinct bands. Legs blackish, 
tibiae yellowish ......... obeonicus. 

(Bengal.) 

83. Subcallus not bare, shining or tuberculous ....... 84 

Subcallus bare, shining tuberculous. ........ 88 

84. Palpi stout. Femora black or reddish brown ....... 85 

Palpi slender. Femora yellowish ......... 87 

85. Forehead two-thirds narrower anteriorly than at vertex. 

Abdomen yellow anteriorly rather transparent. Legs 

yellowish, fore legs darker ....... borniensis. 

(Sarawak.) 

Forehead one-third narrower anteriorly than at vertex. 

Reddish brown or reddish yellow species ....... 86 

86. Abdomen reddish brown. Thorax blackish. Legs black, 

tibiae yellowish wings clear or slightly tinged . . . fuscicauda, 

(Ceylon ; Sumatra.) 

Thorax reddish yellow, almost same colour as abdomen. 
Legs yellowish fore femora darker. Wings tinged yellow 
on fore border ......... uniformis, 

(Malay.) 

87. Abdomen dusky reddish brown or reddish yellow. Forehead 

about a third narrower anteriorly than at vertex, frontal 

callus pear-shaped ....... subhirtus. 



(Bengal ; Bombay ; Java.) 



Abdomen olive coloured. Forehead about half as narrow 

anteriorly as it is broad at vertex, frontal callus very narrow, formosiensis. 

(Formosa.) 

88. Medium-sized species. Abdomen yellowish with darker apex. 

Palpi yellow. Legs reddish yellow, the fore tarsi darker. 

Forehead seven times as long as it is broad. , . tuberculatus. 

(Bengal ; Assam.) 

89. Small species. Legs black tibiae white. Eyes with cross 

bands 90 

90. Reddish brown or yellowish species. Beard white or yellow. 

Palpi usually pale. Forehead ten times as long as it is 

broad simplissimus. 



(Malay ; Sumatra ; Java.) 



288 



MEDICAL ENTOMOLOGY 



Black, sometimes reddish brown species. Beard black. 

Palpi blackish. Forehead eight times as long as it is broad, ceyloiiicus. 

(Ceylon ; Malay ; Sumatra and Java.) 



Therioplectes. 

Group XL 

Species with hairy eyes and tubercle on vertex. 

91. Forehead with two transverse calli. Subcallus bare and 

shining. Abdomen black with white haired bands. . . subcallosus. 

(North India.) 

Forehead with one callus. Subcallus not bare or shining .... 92 

92. Frontal callus black, club-shaped, with spindle-shaped exten- 

sion. Abdomen black, reddish yellow at sides of first two 
or three segments. Palpi stout with short apex. Appendix 
usually present. Legs black and reddish yellow . . . hirtus. 

(North India.) 

Frontal callus small, indistinct. Abdomen blackish, only 
reddish on second segment. Palpi slender with long acute 

apex. No appendix to wing ......... 93 

93. Smaller species. Legs black and reddish yellow . . . wyvillei. 

(Naranda, Himalayas, where it bites human beings.) 
Frontal callus broad, yellow. Abdomen black, reddish yellow 
at sides. Palpi slender. No appendix to wing. Legs 

yellow albilateralis. 

(Java.) 

Tahauus sfriattis, Fabr. A medium-sized fly ; antennae yellowish red, 
darker at their apices ; palpi pale yellow. Frontal callus oblong, not 
quite touching the eyes in front and receding from them behind ; 
for a short distance it is not more than a fine line, afterwards broaden- 
ing out ; the vertical extension often starts from the callus as a broad 
stripe. Thorax brown with four distinct greyish lines. Abdomen 
long and slender, reddish to blackish brown in colour. The medium 
light stripe extends to the sixth segment, and is formed of oblong 
spots, narrowest at their apices. The lateral light stripes extend to the 
fourth segment, and there is often an additional spot on the fifth 
segment. Male with a broad bluish grey band, intersected by a narrower 
band, running across the eyes ; abdomen markedly pointed, with lateral 
pale stripes extending to the third segment only. A common species, 
widely distributed in India. 

Tabanus albimediiis, Walker. A large species with a broad abdomen. 
Antennae reddish, with dark apices ; palpi pale yellow. Frontal callus 
not quite reaching the eyes, with a narrow linear extension. Thorax 
reddish with indistinct grey lines. Abdomen reddish brown with a light 
median stripe extending the whole length; the area on the first segment 



PLATE XL 




289 



Fig. 3. 



PLATE XL 



Figure 1. Tabaiius speciostis, 3. x 3, 

Figure 2. Egg mass of same ; note the chalky substance obscuring 
the eggs. 

Figure 3. Tabanus speciosus, 2 . x 3. 



INDIAN SPECIES OF TABANUS 



289 



small, that on the second flask-shaped, the remaining areas of the 
stripe triangular ; the lateral stripes extend the whole length, but 
are broadest on the second segment. The male is difficult to distinguish 
from that of striatiis : it is darker, and the brown intersecting band 
across the eyes is much wider ; the median abdominal light stripe is 
much broader in parts and is not so uniform. This is one of the com- 
monest Indian species, and occurs almost all the year round in Madras. 

Tabaniis speciostis, Ricardo (Plate XL). A large handsome fly, which 
may at first sight be confused with albimediiis. Antennae reddish, with 
dusky tips ; palpi yellow with many black hairs. Frontal callus oblong, 
not reaching to the eyes, its backward extension narrow, sometimes 
indistinct. Thorax greyish red or brown, with five distinct grey stripes, 
the median one very narrow. Abdomen brownish black with a median 
light stripe consisting of five spots, of which the first is small, the second 
flask-shaped, the third triangular, the fourth triangular but broader, the 
fifth nearly oblong. There are four lateral pale spots, of which the first 
is indistinct, the others well marked and obliquely elongated. Male very 
similarly marked, except that the median stripe is less distinct and 
that there is no lateral spot on the fourth segment. Eyes with a broad 
intersecting band, which becomes narrower at the sides. This is a 
rather rare fly in Madras. It feeds on cattle side by side with the other 
two species. 

Genus Chrysops, Meigen. 

Small Tabanidae with long antennae and banded and beflecked wings. 
The males are somewhat differently marked to the females. In the female 
the eyes are bare, and are widely separated ; there are three well marked 
ocelli on the vertex, and shining black tubercles on the face. The second 
joint of the antenna is usually as long as the first ; the third is four- 
jointed and simple. The palpi in the female are long and bullet-shaped ; 
in the male they are short and stumpy. Thorax as broad as the head. 
Abdomen ovoid, with yellow bands and dark stripes. The wings are 
dark and are ornamented with brown cross bands. 

The conspicuous markings of the flies of this genus, their long antennae 
and well marked ocelli, render them easy to recognize. The eyes in the 
females of many species exhibit in life the most brilliant patterns of 
green, purple and gold, and are most beautiful objects ; the same mark- 
ings are often present in the lower smaller-facetted area of the eyes of 
the male. In some species the eyes are very large and are markedly 
37 



290 



MEDICAL ENTOMOLOGY 



holoptic ; in others they are distinctly small and more or less 
dichoptic. 

The species are abundant in the Ethiopian and Oriental regions, and in 
North and South America. As a group they are retiring in their habits ; 
they are found chiefly in well-wooded localities and in low lying shrub 
in the vicinity of water. The females are blood-suckers, and feed upon 
cattle and horses. 

Miss Ricardo gives the following Key to the Oriental species : — 



Key to the Oriental Species of Chrysops 



6. 



Wings with a dark transverse band and an apical spot 
Wings with a dark transverse band but with no apical spot 
Wings with a hyaline sinus on the posterior part of the band 

in the fifth posterior cell ....... 

Wings with no hyaline sinus on the posterior part of the band 

in the fifth posterior cell ...... 

Abdomen blackish, yellow at apex, with grey bands on the first 

two segments and a grey median stripe ... 

Abdomen yellowish with black stripes . . . , 

Abdomen black, whitish, or yellowish at base 

Discal cell hyaline. Abdomen with four long black stripes 

Discal cell not hyaline ....... 

Abdomen with a short black bifid stripe on the second segment 
often extending to the third or fourth segment 

(Widely distributed in India ; Ceylon ; Malay 
Abdomen with a bifid stripe on the second segment and a 
network of black markings on the third segment, leaving only 
three yellow spots free ....... 

(North Ind 

Abdomen whitish on the first four segments, apex black 

Abdomen black, the first two segments largely yellow, the 
second and third segments with small median spots. Face 
yellowish. Apical border of band of wing straight, concave. 

Abdomen black, the second segment yellowish on fore border. 
Face blackish. Apical border of band of wing straight 

Small species, abdomen blackish, the first two segments yellow 
anteriorly. Face black ....... 

Large robust species. Abdomen blackish with paler median 
spots, largely yellow on the basal segments. Face yellowish. 
Apical border of wing irregular ..... 



2 
I 1 

3 
7 

manilensis. 

(Manila.) 
4 
6 

miokosiewiczi. 

(China ; Japan.) 

5 

dispar. 

and adjacent parts.) 



designata. 

ia ; Western China.) 
rufitarsus. 

(Java.) 



translucens. 

(Malay : Java.) 

pellucida. 

(South India.) 



alter. 



(Borneo. 



Sinensis. 



(China.) 



PLATE XLI 




291 'Fig. 2. Chrysops dispar, ? . x 7. 



ORIENTAL SPECIES OF CHRYSOPS 291 



7. Wings with a clear spot in the discal cell, first joint of the 
antenna slightly incrassate. Abdomen blackish with pale 
spots ........... 



stimulans. 



Wings with no clear spot in the discal cell . . . . 
8. Band of wing broad throughout. Abdomen yellow with a 
black bifid stripe in the second segment .... 



(Bengal.) 
8 



Indiana. 



(South India ; Assam.) 



Abdomen yellowish, with a black band in the middle 
Abdomen yellowish, with two distinct black bands 
9. Abdomen with blackish legs and face 



fasciata. 



9 
10 



(Malay ; Java ; Sumatra.) 



Abdomen with yellowish brown legs and face 



fixissima. 



10. Abdomen with the black bands narrower 



(Ceylon ; Sarawak.) 
signifer. 



(Philippines.) 

Abdomen darker, the black bands broader .... cincta. 

(Malacca ; Philippines.) 
11. Abdomen black with a yellowish band on the second segment. 

Small species flavocincta. 

(Assam ; Ceylon ; Sarawak.) 

Chrysops dispar, Fabr., (Plate XLI, tig. 2) is a common South Indian 
species, easily distinguished from the others by the colouration of the 
abdomen, which is yellow, with a dark bifid stripe commencing 'on the 
second segment and extending to the fourth. Chrysops dimidiata, van 
der Wulp, a West African species, is said to enter houses and to bite 
man. 

It has been announced recently that Leiper has demonstrated that 
the development of Filaria loa is completed in the salivary glands 
of a species of Chrysops in Calabar, Southern Nigeria. 



Medium sized or small flies with elongated bodies and with light and 
dark markings on the icings. Head transversely oval, and distinctly 
broader than the thorax; the eyes may be hairy or nude; in the female 
they are widely separated. The antennae are three-jointed ; the first 
joint is thick and moderately long, the second very short, the third longer 
than the first two together, and consisting of three segments incompletely 
separated from one another. The thorax is rounded and may be marked 
with bands or spots. The abdomen is elongated with parallel sides. 
The wings are long and of a dark brown or black colour, and may have 
three or more rosettes formed by pale marks on a darker ground colour. 

In most of the females of this genus the eyes are highly coloured, and, 
as the markings have been employed to a considerable extent in 



Genus Haematopota, Meigen 



292 



MEDICAL ENTOMOLOGY 



separating the species from one another, they should be noted in the 
fresh condition and recorded. As a rule the eyes of the males have no 
bands on the dorsal portion, but are marked like those of the female 
in the lower area where the facets are smaller. 

The flies of this genus are widely distributed, and many of the species 
are common where they occur. Haematopota phivialis, L., which is 
figured on Plate XLI, is perhaps the commonest European species. A 
large number are found in the tropics, Africa being notably rich in species. 
According to Neave the African species are more abundant in higher 
localities; they have been found at an altitude of 10,000 feet. Neave 
points out in a recent paper that the East African species are somewhat 
irregularly distributed, being abundant in some parts and rare in others, 
and that the season in which they are prevalent is very short. He 
shows that the lighter species are found mainly in open short grass 
country, while the darker ones are confined to well-wooded localities in 
the vicinity of streams. 

Genus Silvius, Meigen 

Medium-sized flies with clear hyaline wings. Antennae short, the 
second Joint much shorter than the first; the third segment has a well 
developed dorsal tooth at its basal end, and consists of four segments. 
The eyes are uniformly coloured and the facets are all of one size in 
both sexes. 

The species of this genus are widely distributed. The females are 
blood-suckers, but are not aggressive unless their haunts are approached. 
Neave states that the female of S. fallax, Austen, frequents water holes 
and attacks the natives as they go to draw water. 

Genus Cadicera, Macquart 

Large robust flies with dark xcings. The head is flattened antero- 
posteriorly. The abdomen is broadened laterally, and is generally 
brightly coloured. Antennae three-jointed, simple, and without a spur ; 
the distal joint has seven annulations. The proboscis is as a rule longer 
than the head. 

Most of the species of this genus are confined to South Africa, but 
some have been recorded from other parts of the same continent. One 
species is known from Nyasaland, and another, C. speciosus, Austen, 
has been found by Neave in German East Africa ; the latter was taken 
in wooded country at the foot of Mount Kifulufulu, and was seen to bite 
cattle. 



GENUS PANGONIA 



293 



Genus Pangonia, Rondani 

The flies of this genus are distinguished by the rennarkable long 
forwardly-directed proboscis. The great majority of the species, per- 
haps all, are flower feeders. The genus has been divided into five sub- 
genera, according as to whether the first posterior cell is open or closed, 
the eyes bare or hairy. 

Pangonia (sensu restr.) Most of the species included in this sub- 
genus are large insects with hairy bodies. The antennae are simple, 
the first joint short, the third long, with seven annulations. The pro- 
boscis is long and slender, and may be as long as the body of the fly ; 
that of P. rostrata, for instance, is one and a half inches long. There is 
evidence that some of these flies, notwithstanding the great length of 
the proboscis, feed on mammalian blood ; they do so, not by settling on 
the skin in the ordinary manner and inserting their biting parts deliber- 
ately, but while hovering near by, making sudden darts ; to obtain a full 
meal it must be necessary for them to repeat the manoeuvre many times. 
Such a habit is apparently exceptional in the genus, as in the majority 
of cases the mandibles and maxillae are shorter than the labium, and 
cannot, therefore, be employed in making a wound. The species are 
mainly found in the Ethiopian region. 

Erephrosis, Rondani. In this subgenus the first posterior cell is 
closed and the eyes are hairy. The species are found in South America 
and parts of Australia. Lutz and Neiva have recently described a beauti- 
ful golden species from Brazil. It is not known whether they are blood- 
suckers or not. 

Sub-PANGONIA, Sourcouf. This subgenus closely resembles Pan- 
gonia, except as regards the proboscis. This is short or moderately 
long, and is thick and fleshy ; it is bent downwards at an obtuse angle. 
The labella are as long as the proboscis, and are conspicuously thickened. 
On the superior margin of the inner surface of each labellum there are ten 
rod-like structures, thick at the base and pointed apically, which Sourcouf 
thinks are almost completely closed tubes which assist in suction. Austen 
states that Dorcaloemiis silverlocki, Aust., and Pangonia comata, Aust., 
have homologous structures on their labella. Only two species of Sitb- 
pangonia are known, S. gravoti, Sourcouf, and S. grahami, Aust., the 
former from the French Congo and the latter from Southern Nigeria. 
They may be mistaken for humble bees, as they have the habit of 
hovering in the air, and their flight is accompanied by a bee-like 
buzz. 



294 



MEDICAL ENTOMOLOGY 



DiATOMlNEURA, Rondani, and CORIZONEURA, Rondani, are found in 
the Ethiopian region, the latter also in the Oriental region. They are not 
aggressive blood-suckers, and are found in well-wooded districts. 

Genus Dorcaloemus, Austen. The flies of this genus have bare eyes 
and have the posterior cell closed. They are not aggressive biters. The 
genus is limited to South Africa. 

Genus Rhinomyza, Wied. This genus has a superficial resemblance 
to Chrysops. The antennae, however, resemble those of Tahaniis, the 
basal hook being well marked. Ocelli are present, and the hind tibiae 
have spurs. They are found in Africa, Java and South America. 
Neave states that they frequent shady places and feed most frequently in 
the evening. 

The remaining genera of the Tabanidae are distributed as follows : — 
Udenocera, Ricardo, Ceylon. — Neotabanus, Ricardo, Ceylon. — Diach- 
loriis, Osten Sacken, North and South America and the 

° TabaSr °^ Philippines.— Lepidoselaga, Macquart, Brazil, Australia 
and Chili. — Stibasoma, Schiner, Brazil. — Dasybasis, 
Macquart, Australia and Chili. — Bolbodimyia, Bigot, Venezuela. — Acan- 
thocera, Macquart, South America. — Dichelacera, Macquart, South 
America. — Apocampta, Schiner, Australia. — Dicrauia, Macquart, Brazil. 
Pifyocem, Gigl-Tos, Central America. — Goniops, Aldrich, North America. 
— Apafolestes, Williston, North America.- — Pelecorhynchits, Macquart, 
South America and Australia. Pronopes, Loew, Cape of Good Hope and 
Java. — Eseiibeckia, Rondani, Brazil. — Gasfrixodes, Saunders, India. — 
Adersia, Austen, South Africa, — Aegophagainyia, Austen, Zanzibar, 
Rodrigues, and Astove Islands ; British East Africa. — Bovierella, Surcouf, 
Madagascar. — Scepsis, Walker, South America. — SeJasoma, Macquart, 
South America. — Scioiie, Walker, Seychelles, South America and 
Australia. 

When studying the feeding habits of the blood-sucking Tabanidae 
it is useful to have a tame cow or horse, and to tether it in a field or 
some well-wooded place in the vicinity of water in a 

Bionomics of the j^^^u^ ^.^ich the flies are known to occur. In a 
Tabanidae 

short time one or more of the females will alight on it 
and commence sucking blood. The different species which have been 
observed under such conditions in Madras show a remarkable peculiarity 
in the selection of the site from which to feed. T. specious and T. albi- 
mediiis almost invariably settle low down on the back of the hind leg, 
while T. striatiis and T. hilaris frequently select the same site, but may 
also be seen biting on the under surface of the abdomen, particularly on 



FAMILY TABANIDAE : BIONOMICS 



295 



the flap of skin near the navel. T. bicallosiis seldom settles on the 
lower parts of the body but nearly always on the sides of the neck or 
abdomen. T. ditaeniatus is most often seen biting on the udder, some- 
times however, it will settle on the side of the neck. Chrysops dispar 
generally chooses the inner sides of the fore legs, and Haeinatopota the 
hump or the neck. 

If one of these flies is watched closely as it feeds, it will be noted that 
as it becomes replete with blood it passes out a dark fluid — if it has fed 
recently — which drops on to the hair of the host. Next a clear fluid 
is voided, and last of all apparently unaltered blood. All this fluid 
collects in droplets on the hair below the fly. The moment it withdraws 
its proboscis one or two large drops of blood trickle out of the wound and 
mix with the excreta. It is not unusual to see two or even three flies 
feeding at the same time close together. These habits probably explain 
how tabanids become infected with their natural flagellates {Crithidia 
and Herpetomonas). A fl}- which sucks blood at the spot where 
the excreta of another has been deposited must necessarily contam- 
inate its labella when they are pressed against the skin just before 
the wound is made. Immense numbers of flagellates are passed out in 
the fluid excreta of an infected fly, and it is not difficult to understand 
how another fly may suck them up. For the description of the method 
of feeding, see page 27. 

On leaving the host the flies usually settle on the under surfaces of 
leaves, the barks of trees, stones, or the walls of an adjacent building ; 
they remain here for several hours, and later collect in the vicinity of 
water. Judging from experiments carried out with tabanids kept in cap- 
tivity, they appear to feed every three days. It is not definitely known 
whether copulation takes place before the first feed of blood, but it 
would appear that fertilization is in some way connected with the subse- 
quent food of the female. No satisfactory explanation can be offered as 
to why bred females can hardly ever be induced to suck blood, even when 
they are placed in a large enclosure along with cattle. It is interesting 
to note Neave's observations on the habits of these flies when the males 
predominate. He says, ' I think it very probable that female Tabanidae 
' will be found to feed on blood only during a certain period of their imago 
' stage. This period seems to be subsequent to pairing and to the death 
' of the male individuals, and most probably (though I have no actual 
' evidence of this) before oviposition '. Although numbers of both sexes 
of T. albimediiis and T. striatus have been kept in large cages by the 
writers, under as near as possible natural conditions, the act of copulation 



296 



MEDICAL ENTOMOLOGY 



has never been seen, and the majority of the females would not suck blood. 
It is not known how long a tabanid lives under natural conditions. 
Observations on this point would be most valuable. 

Hine records having seen T. siilcifroiis in copulo about 8 a.m. ; the 
male clings to its perch, and the female hangs suspended with its legs 
and wings motionless ; the whole act lasts about ten minutes. When 
disturbed the male flies a short distance, and soon alights either on the 
ground or on some low-lying foliage. 

It has frequently been noted that tabanids are in the habit of flying 
over water, and darting down and striking the surface; these manoeuvres 
are not very clearly understood, but Hine appears to think that both 
sexes behave in this way and that they are merely sipping water. Hine 
also considers that the female tabanid takes much food other than blood, 
and that some may even pass their whole existence without taking blood 
at all ; he has examined the alimentary tracts of both sexes and found a 
yellow fluid, indicating that something else besides pure water or blood 
had been imbibed. 

The Tabanidae always lay their eggs in the vicinity of water, and the 
flies are never found very far from it. The habits of those species which 
have been studied show that there is considerable 

amf^EarW Stages '^^^'"i^.tion in the methods of egg-laying. Some species 
oviposit almost entirely on particular plants, while 
many do not select any special plant. The position in which the eggs 
are deposited with respect to the depth of the water depends to a large 
extent on the structure of larvae ; this is a point which would repay further 
study. 

Hine has described the egg-laying habits of Tabanus sfygius, Say, which 
always oviposits on the upper surfaces of the leaves of the arrow plant, 
placing the eggs above the point where the petiole meets the expanded 
part of the leaf. Hine goes on to say : ' So closely is this habit fol- 
' lowed that a hundred masses of eggs are found thus located, to one placed 
' otherwise. Sometimes a mass is observed on a leaf of another plant, but 
' in the same location, and once in a long time eggs are seen in a different 
' location of a leaf '. The black horse fly, Tabanus atratits, Fabr., places 
its eggs on a particular species of sedge in low ground near swamps or 
ponds. Chrysops callidiis, Osten Sacken, arranges its eggs in a single 
layer on leaves of various kinds of plants overhanging water in ponds and 
small lakes ; C. moerens, Walk., oviposits is similar places. 

King has recently recorded the egg-laying habits of several Soudanese 
tabanids; Tabanus par, Walk., and T. taeniola, Pallisot de Beauvois, for 



FAMILY TABANIDAE: BREEDING HABITS 297 



instance, lay their eggs on the leaves of water \\ eeds, and on blades of 
grass. Tabaiiiis hingi, Aust., lays its eggs on rocks over deep pools. 

In Madras, Tabaniis albiinediiis, Walk., oviposits in a variety of situ- 
ations, but most frequently on the leaves of some plant overhanging deep 
water. Its egg masses have also been found on small rocks in the bed 
of a stream, and on pieces of string hanging over house drains ; on 
one occasion a mass was found on a Papaya tree, at the foot of which 
water was occasionally allowed to flow. Tabanus speciosiis, Ricardo, 
always lays its eggs on the leaves of water lilies growing in deep water. 
Tabanus sfriatiis, Fabr., oviposits as a general rule on blades of grass, 
pieces of stick, etc., at the edge of a river, stream or pond ; Tabanus 
hilaris, Walk., has the same habits. Chrysops dispar, Fabr., Tabanus 
ditaeniatus, Macq., Tabanus bicallosus, Ricardo, Tabanus virgo, Wied., 
and two undetermined species of Haematopota, all of which are small 
tabanids, invariably lay their eggs on blades of grass just aLthe edge of a 
shallow stream, or on the leaves of the lotus plant at the edges of small 
ponds, but never over deep water. 

The position selected by any one of these flies to deposit their eggs is 
not a chance one. The larvae of the larger tabanids, such as albimedius, 
striatus, and speciosus, are powerful swimmers and have air sacs con- 
nected with their tracheal tubes, so that they can float or sink at w ill. The 
larvae of the smaller species in Madras are devoid of these air sacs, so 
that if they fall into deep water they die. It is important to recognize 
this in breeding experiments and to place them in tra}-s with only a little 
water. 

The number of eggs laid by the different species is also of interest. 
T. albimedius and T. speciosus lay between 500 and 600 eggs, while the 
smaller species lay about 300. When one of the larger species is 
about to oviposit it alights on the leaf or blade of grass with its head 
downwards ; it then thrusts the tip of its abdomen forwards under its 
thorax, and deposits an egg, \\ hich adheres to the leaf owing to the 
stick}^ substance which accompanies it. The abdomen is then returned 
to its original position, and as soon as the next egg is ready to be 
laid, is again flexed, and the second egg is placed at one or other 
side of the first. In this way three or four eggs are laid on one side of 
the first and three or four on the other. The mass at this stage has the 
shape of a V. The fly now moves forwards, and, raising the end of her 
abdomen to one arm of the V, places a number of eggs down the side 
.until the apex is reached ; she then changes over to the other side and 
deposits eggs all down that arm up to the apex. In the end a raised 
38 



298 



MEDICAL ENTOMOLOGY 



compact mass of eggs is built up, which, if examined with a lens, demon- 
strates the precision with which the eggs are placed in reference to one 
another. 

It is often possible to watch a female tabanid with a hand lens while 
she is laying her eggs without disturbing her ; sometimes it is even 
possible to break off the leaf or twig and to carry her some distance to a 
laboratory, where she will continue to lay her eggs. 

In Madras all the smaller species of Tabanits, as well as Chiysops 
dispar and the two species of Haeinatopota referred to above, spread 
their eggs out in one or more layers on blades of grass ; in some instances 
they are moulded into the hollow of the blade right up to the tip (Plate 
XLII, figs. 2, 11 and 12). Tahaniis speciosiis (Plate XL, fig. 2), 
instead of forming a V-shaped mass as is usually the case with the 
larger tabanids, lays its eggs in a round heap, which it then plasters over 
with a chalk-like substance, almost completely covering the eggs. 

The eggs of all the smaller tabanids in Madras are torpedo-shaped, 
while those of the larger species, such as aJhimediits, are sub-cylindrical 
with tapering ends. The eggs of Tabaiiiis hicallostis, a small species, 
measures I'l mm. in length and "2 mm. in breadth, that of ditaeniatus is 
about 1'2 mm. in length and also '2 mm. in breadth ; the eggs of alhimedius, 
a larger fly, measure 1'9 to 2 mm. in length and '4 mm. in breadth. 
Most of the eggs of the smaller species are white when first laid, but 
they soon become dark. Those of one species of Haeinatopota are dark 
grey when deposited, while those of alhimedius, striattis and liilaris are 
brownish white. 

The egg masses of tabanids are often parasitized by small species of 
hymenoptera which oviposit in them. Plianarus tabanivonis, Ashmead, 
is common in the United States, where, according to Hart, it parasitizes 
a large number of the egg masses of Tabanits at rat us. Telenomiis 
benefactor, Crawford, is another chalcid which parasitizes the eggs 
of tabanids in the Soudan. In Madras a similar insect, which has 
not been identified, regularly destroj-s large numbers of egg masses of 
albimediiis and striattis, A parasitized egg mass can be recognized by 
the almost black colour which it assumes when the development of 
the embryos of the hymenopteron is almost complete. 

In Madras the smaller species of Tabanidae ah\ a} s lay their eggs in 
the afternoon, commencing about 4 p.m. : Clirysops dispar has been 
seen ovipositing as late as 7 p.m. The larger species, on the other hand, 
lay their eggs any time during the day, but as a rule in the morning. 
The larvae hatch out in from four to seven days after the eggs are laid ; 



PLATE XLII 



Figure 1. 
Figure 2. 
Figure 3. 



Figure 


4. 


Figure 


5. 


Figure 


6. 


Figure 


7. 


Figure 


8. 


Figure 


9, 


Figure 


10. 


Figure 


11. 


Figure 


12. 


Figure 


13. 


Figure 


14. 


Figure 


15. 


Figure 


16. 



Two eggs of Tabanus bicallosus. 
Egg mass of the same laid on a blade of grass. 
Eiglith abdominal segment of pupa of male of same, 
showing the six large tubercles. Note the ribbed anal 
tubercle and the continuous fringe of spines in 
front of it. 

Eighth abdominal segment of pupa of female of same. 

Note the simple anal tubercle and the interrupted 

fringe of spines in front of it. 

Mature larva of Tabanus bicallosus. X3. 

Pupa of same, x 4. 

Mature larva of Tabanus ditaeniatus. Note the 
short stout syphon tube. X3. 
Pupa of same, x 4. 

Eighth abdominal segment of pupa of same. 
Egg of Tabanus ditaeniatus. 

Egg mass of the same Hy spread out m a single layer 
on a blade of grass. 

Egg mass of Chrysops dispar, on a blade of grass; 
also a single egg enlarged. 

Mature larva of Tabanus virgo. The openings of the 
tracheae are flush with the body, x 4. 
Pupa of same, x 5. 

Small egg mass of same laid on a dried twig. 
Eighth abdominal segment of pupa of same. 



FAMILY TABANIDAE: EARLY STAGES 299 



first one larva wriggles out and very soon afterwards the others emerge 
and the mass is transformed into a collection of larvae struggling to 
free themselves ; they drop singly or in heaps into the water or wet 
mud, and quickly bury themselves out of sight. The recently hatched 
larva is almost pure white, and both ends are, as a rule, pointed. 

The body of the mature larva is cylindrical, tapering at both ends, 
and consists of eleven segments excluding the head ; its skin may be 

blotched or streaked in the form of stripes or bands. 

'Tu i 4.U ■ i. J u 1 • • i. u • External structure 

Ihe antennae are three- lomted, the basal lomt bemg , . , 

° of mature larva, 

short, and are attached to the anterior angles of the pi^te XLII 

head just above the palpi ; a bunch of stiff spines, either 

short or moderately long, is situated just above each antenna and on each 

side of the labrum. The segments of the body are whitish or striated, 

and the prothorax has a groove on its ventral surface. Each segment of 

the abdomen has a Y-shaped group of punctures and is encircled 

anteriorly by a horizontal ridge beset with fine hairs. There are two 

prominent fleshy tubercles at each lateral angle, and four, arranged in 

pairs, on the ventral surface. The last segment has a bilobed anal 

prominence bounded posteriorly by a semicircular ridge covered with 

hairs. The vertical stigmal plate is situated at the apex of a conical 

retractile prolongation, the syphon tube. 

The mouth parts of the larva are adapted for seizing the prey, and 

constitute a very formidable apparatus. The essential organs are the 

mandibles and first maxillae, and of these the former 

r 1 11 , mouth parts 

are the most powertul weapons. Each mandible is a 

stout rod of chitin, slightly expanded at the base, to which the muscles 
are attached, and narrowed distally to a blunt point ; the rod is curved 
downwards and forwards, and is armed on its concave border with many 
coarse serrations. The maxillae are similar in shape and general dispo- 
sition, but are smaller and less heavily pigmented, and are more pointed. 
Both pairs of appendages can be thrust out of the head in a downward 
and forward direction when the larva attacks its prey, by means of the 
protractor and retractor muscles attached to the bases of the rods. One 
sometimes becomes unpleasantly aware of the existence of these organs 
when handling the larvae, as they are used in defence as well as in 
attack, and are capable of inflicting a sharp nip, though they do not 
draw blood. The maxillary palps are simple and two-jointed, the distal 
joint being much smaller than the proximal one. The dorsal and distal 
extremity of the head is produced forwards as a short and fleshy 
labrum. 



300 



MEDICAL ENTOMOLOGY 



The pharynx is an elongate chitinous chamber of the usual type, and 
is easily seen in the living larva. It leads posteriorly to the oesophagus, 
which is wider and more muscular than that of the 
The Aiimentary ^^^^j^. . -j. ^^^^ ^j^^ oesophagus is wider 

Plate L, fig. 1 more muscular m msects whose food is solid or 

semi-solid than in those which take only fluid food. 
The oesophagus opens into a short and cylindrical proventricuhts, which 
is also, a highly muscular structure, and is sharply distinguished from 
the succeeding part of the gut by its clear translucent appearance in 
the fresh condition. The mid-gut extends from the proventriculus to 
the hind end of the body, and is thrown into one or two simple coils, 
not constant in their position. It is separated from the proventriculus 
by a short constriction, and is again constricted at the posterior end, 
just anterior to the opening of the Malpighian tubes. Between these 
points the lumen is wide, and is thrown into numerous sacculations by 
the contractions of the muscle fibres in the wall. The mid-gut is of a 
very striking orange red colour in the fresh condition, and is filled with a 
semi-solid mass of a light chocolate colour, which oozes out if the wall 
is punctured in dissection. The hind-gut is short and simple, and is 
coiled up in the posterior end of the abdomen. The total length of the 
gut is about twice the length of the body of the larva. 

To dissect out the alimentary tract : — Pin the larva down in a dissect- 
ing trough, extending it as much as possible. Then take a pair of 
fine forceps and pinch up a portion of the integument near the anterior 
end, and cut it with a pair of fine scissors. Once the initial incision 
has been made it is easy to cut a strip of the integument away from the 
rest, carr}'ing the incision to the opposite end of the body. The large 
lateral tracheae should now be torn off at -the posterior end and removed. 
The whole of the alimentary tract is then exposed, and is easily sepa- 
rated from the integument, to which it is only attached by a few tracheal 
twigs. 

The salivary glands are simple and tubular, and bear a remarkable 
resemblance to those of the adult insect. 

The respiratory system resembles that of the mosquito larva. There 
are two large lateral tracheae which run the whole length of the body, 
on each side of and slightly dorsal to the alimentary 

The Respiratory These communicate with the external air 

System 

through an opening, w hich can be closed, on a small 
eminence on the dorsal surface of the penultimate segment. As they 
pass forward they give off branches for the supply of the tissues in the 



GRABER'S ORGAN : THE PUPA 



301 



ordinary manner ; they are not, however, simple tracheae, but are rather 
of the nature of air sacs, as their diameter in most species is distinctly 
greater than would suffice for their main function of conveying air 
to the tissues, and contracts suddenl}-, w ithout the giving off of any 
branches, at the anterior end. In some species such dilatations are 
not present. 

At the posterior end of the larva of Tabanits there is a curious struc- 
ture, the function of which has not been determined. It consists of a 

small pear-shaped sac, the broadest end of which is 

... Graber's organ 

anterior ; the posterior end narrows down to a tine 

tubule, which opens on the integument of the body between the last 

and the penultimate segment. Within this sac there is a series of 

capsules set one behind the other in the long axis, and within each of 

these capsules a pair of small black pyriform bodies, each attached 

to the anterior side of the capsule by a delicate pedicle. These bodies 

diminish in size from the anterior end, the first being considerably larger 

than the rest. They are easily seen through the integument in the 

living larva. Graber believed that the structure is a sense organ, but 

Berlese does not consider that this has been proved to be the case. 

It is well supplied with nerves. The outer sac is an invagination of 

the integument, and as such has a chitinous lining. 

The pupa is sub-cylindrical, abruptly pointed anteriorly, and tapering 

somewhat posteriorly ; it is generally yellowish brown to ferruginous 

brown, finely wrinkled, and has a lateral tuft of hairs 

on each abdominal segment. On either side of the «, ,T''f.i'"*!f"„ 

° XLII, figs. 6, 8 and 14 

head are the antennal sheaths, pointing outwards, and 
on each side of the median line two large tubercles, each with a central 
hair ; below these there are two raised areas with sharp edges, separated 
by a deep ridge. Lower still there is a pair of elevations, also with 
raised edges, and on the ventral surface of the head one or more tuber- 
cles. The segments of the thorax are indistinct ; the mesothorax bears 
the large, raised ear-shaped spiracles. The abdominal segments arc 
free and about equal in length, and have one or more hairs near their 
hind margins ; the second to the seventh segments inclusive have well- 
marked lateral ridges, covered with long hairs which are continued into 
the dorsal and ventral surfaces. These hairs increase in length from 
before backwards, and are best developed on the seventh segment. The 
eighth segment is short, and is armed with six projecting spurs or teeth, 
and with a large anal tubercle. In the male the tubercle is ribbed and 
bounded anteriorly by a continuous fringe of strong spines ; in the female 



MEDICAL ENTOMOLOGY 



the tubercle is smaller and the fringe of spines is broadly interrupted 
(Plate XLII, rtgs. 3, 4, 9 and 16). The pupae of many of the larger 
species of Tabaniis have in addition a lateral tuft of spines situated 
on a ridge. 

Tabanid larvae grow very slowly, feeding at first on small crustaceans, 
which are abundant in water and moist earth ; they soon, however, 
attack and destroy each other, and this is one of the greatest obstacles 
in breeding experiments. In Madras, the larvae take from two and a half 
to three and a half months to become mature, and then they pass through 
a short or long resting stage, during which time they do not feed. The 
pupal stage lasts from ten days to a fortnight. From numerous experi- 
ments with the Madras species it has been found that the complete life 
history from the egg to the imago lasts from four to five months, and that 
there are usually two broods during the year. In other countries the 
length of life history varies, and the larvae of many species hibernate 
during the cold weather. The larvae of the larger species and the nearly 
full grown stages of the smaller species feed almost exclusively on earth 
worms, whose body juices they suck out ; this explains how gregarine 
cysts {Monocystis) are not uncommonly found in the alimentary tract of 
the imagines. 

The larvae of the different species are very like each other, and 
it is often dii^icult to distinguish the mature larvae of the smaller flies 
from the young larvae of the larger species. The points to be noted 
are : — the abdominal markings, such as the presence or absence of 
striae, the character of the pseudopods, the length of the syphon tube, 
and the structure of the antenna. In the case of the pupa the 
following points should be noted : — the length of the antennal sheath, 
the character of the thoracic spiracle, particularly its inner margin, 
the length of the hairs on the abdomen, the structure of the abdominal 
spiracles, and the shape and size of the spines and teeth on the eighth 
segment. 

There should be no difficulty in finding the larvae of any of the 
Tabanidae in a locality in which the flies are common. It is, as a rule, 
only necessary to collect the wet mud from the margin of the nearest 
patch of water and place it in a bucket or kerosine oil tin. Water is 
then added in sufficient quantity to form a thin fluid. The larvae of the 
larger species, if they have air sacs, will at once float up to the surface of 
the water. The muddy water should now be thoroughly stirred up and 
then poured through a large circular sieve with a fairly course mesh ; if 
there are any larvae in the mud they will be caught by the sieve. This 



BREEDING TECHNIQUE 



303 



is the quickest way of finding these larvae, and in a locality where they 

are plentiful many hundreds may be collected in a short time ; it should 

be remembered that the mature stages of some species travel long 

distances awaj' from the edge of the ^\•ater over which the eggs were laid, 

and may be found in almost dry mud. The pupae are always found at 

some distance from the water, just below the surface of the earth ; they 

are difficult to recognize. Digging up mud from the edge of a pond or 

river with a stick, and turning it over bit hy bit is tedious and never 

gives such good results. 

The student of medical entomology owes much to Professor Hine's 

pioneer work on the breeding of the American Tabanidae. Since his 

papers were published work of a similar nature has _ .. _ . . 

. , Breeding Technique 

been carried out m the Soudan by Kmg, and Howlett 

has bred some species at Pusa in Bengal. By using Hine's methods of 
rearing the immature stages in glass jars of various sizes it is possible to 
breed out a few flies, but large numbers cannot be raised. As the larvae 
very soon begin to destroy each other, hundreds of bottles, each to con- 
tain a single larva, are necessary ; the work then becomes cumbersome. 
It will also be found that the young larvae when separated into the jars 
are apt to die. The jars are, however, of considerable value when the 
larvae are about three-quarters grown, or when they are about to pupate ; 
at this stage they do not require so much attention, as they are much 
hardier. The use of jars at an early stage of the experiments has, 
therefore, been abandoned and instead large trays have been utilized 
with considerable success. The method of constructing and using these 
trays will now be described. 

A sheet of galvanized iron seven feet long is made into a tray 
about six inches deep by turning up the sides and soldering up the 
corners ; this can be done by any tinsmith. The tray is then tested to 
see that it is water tight. It can be used for rearing the larvae by filling 
it with sand and mud sloped off so as to simulate as near as possible 
the side of a stream or pond (Plate XLIV, fig. 2). Different kinds of 
water plants are now planted in the mud and the tray is about three- 
quarters filled with fresh water, preferably from a stream ; in this way 
about a foot or more of the mud is left uncovered. The water must be 
changed every ten days, and in order to accomplish this a hole should be 
bored in the bottom of the tray near one corner ; a well-fitting cork will 
prevent the water from escaping. It is important" to remember that if 
the mud used in filling the tray is brought from the side of a river or 
pond, it may already contain some large tabanid larvae ; if small larvae 



304 



MEDICAL ENTOMOLOGY 



are put into the tray they will soon disappear, for as noted above tabanid 
larvae are fond of eating their own kind. The mud should first be 
mixed with water and then passed through a sieve, and in this way all 
large larvae will be removed. 

The tray described above can be readily converted into a cage of any 
height by making a framework of stout wire, which is soldered at intervals 
to the outer sides. Mosquito netting is then fitted over this and tied 
securely round the bottom (Plate XLIV, fig. 3). The cage should be placed 
on a table, the legs of which are standing in large tins of water ; it is 
well to place the table away from the wall, and if possible in an eastern 
situation so that it gets a few hours of sunlight in the morning. Great 
care should be taken to see that the net is properly secured round the 
bottom of the tray ; spiders will find their way into the cage, and it is 
more than anno5'ing to find a special fly in the clutches of one of these 
creatures. For the smaller species of tabanid such a large tray is un- 
necessary, and a piece of galvanized iron seven feet long will make two 
smaller cages (Plate XLIV, figs. 1 and 4). 

These cages are suitable not onlj- for breeding tabanids, but also 
for keeping muscids in captivity and for feeding experiments with 
mosquitoes. Tabanids may be kept alive in these cages for at least 
three weeks if they are regularly fed. 

If caught specimens of tabanids are placed in suitable cages, it will be 
found that many of them will lay their eggs, especially if they are taken 
out in large test tubes every three or four days and fed on some 
animal, preferably a cow. 

When an egg mass has been obtained the object on which it is fixed 
should be taken to the laboratory and placed in a small dish of water, 
carefully protecting it from the attacks of ants. As soon as the larvae 
hatch out they should be transferred to one of the trays prepared as 
described above. The}' should on no account be picked up with forceps, 
but drawn up into a glass pipette of suitable bore ; in this wa}' they can 
be easih' counted. About fifty at most should be placed in each traj', as 
if they are well scattered there is less chance of their destroying each 
other. If the water contains weeds and surface plants, the young larvae 
will find small crustaceans and similar forms of life on which to feed ; 
later the tray should be well stocked with earth worms of all sizes, the 
smaller ones being very suitable for the young larvae. 

The great advantage of rearing the larvae in these trays is that they 
require little or no attention except the regular changing of the water, 
the addition of fresh earth worms about every ten days, and the removal 



BREEDING TECHNIQUE 



305 



of dead weeds, or any other decaying matter which is likely to render the 
water very foul. If fifty larvae are placed in each tray, and they are well 
scattered, about one-fifth will reach maturity. At this stage they remain 
in a resting condition without feeding, and should be removed from the 
tray and placed singly in the small jam jars (Plate XLIV, fig, 5) ; each 
jar should have a good screw top, well perforated with holes just small 
enough to prevent the larva from getting out. The jar should contain 
sufficient moist mud to enable the larva to bury itself ; the mud should 
be changed once a week. The removal of the old mud is accomplished 
by filling the jar about half full of water, and stirring up the mixture with 
a glass rod until it is sufficiently fluid ; it is then turned out over a 
coarse sieve, which catches the larva but permits the fluid to pass through. 
The larvae should not be picked up with forceps, and it is well not to 
touch them with the fingers, as they are capable of inflicting a sharp bite 
with their powerful mandibles. 

In due course the larvae pupate, and are then found just at the 
surface of the mud and almost completely covered, at most their dor- 
sal surfaces being exposed. It will be remembered that the imago 
emerges out of the pupal case through a T-shaped slit on the dorsal 
surface of the thorax, and the pupa lies in such a position that this can 
be accomplished without any accident. The pupae should be removed 
from the jars in the same way as the larvae, and placed in small holes 
in moist mud in one of the cages, which is covered with a good 
net. If the pupa is held by its anterior end and the last abdo- 
minal segment inserted just in the hole, it will soon wriggle itself 
into the desired position. A little flag with all the data relating 
to the particular pupa should be fixed in the mud close to it. The 
pupae should be kept under observation in order to secure the flies as 
they hatch out. If some of the larvae are left in the tray and allowed 
to pupate, the pupae will be found some distance from the water ; it is 
not, however, advisable to leave the pupae in a tray containing larvae, as 
they are often killed. 

Attention to all these details is very necessary, for these flies, 
more than any others, require careful handling, or the worker 
will find that though he began with 500 larvae, he will end with 
one or two flies. The secret of success in this work largely lies 
in obtaining as near as possible the natural surroundings of the 
larvae, and in order to do this it is essential to study the habits of 
the flies and to note exactly where, and under what conditions, they 
lay their eggs. 
39 



306 



MEDICAL ENTOMOLOGY 



FAMILY LEPTIDAE 

Flies of moderate or large size with elongated bristly bodies. Vena- 
tion similar to that of the Tabanidae. Antennae very variable, usually 
with three joints ; the third may consist of a number of small segments 
and is with or without a terminal or dorsal arista. Empodium pulvilli- 
form ; tibiae with spurs. Larvae chiefly aquatic and as a rule predaceous. 

According to Austen there are four blood-sucking species belonging 
to three genera. Williston states that one of these, Symphormyia, 
which is found in America, has the habit of sucking blood like the 
Tabanidae. Its first antennal joint is thickened and elongated, and the 
third segment is reniform in shape ; the hind tibiae have a single 
spur, and the anal cell is open as in Tabanus. The proboscis is short 
and stout. 

Two of the other blood-sucking species belong to the genus Leptis, 
namely, Leptis scolopacea and L. strigosa, both of which are found in 
France ; they appear only occasionally to suck blood. The hind 
tibiae of these two flies have two spurs and the third antennal segment 
is not reniform. 

The fourth blood-sucking species belongs to the genus Trichopalgus, 
(T. obscurus), and is found in Chili; it is said to have a long pro- 
jecting proboscis. 

FAMILY PHORIDAE 

Small, often minute, flies with a hunch-backed appearance. The third 
joint of the antenna is often large, concealing the other segments, and 
is spherical and often pointed, with an apical or subdorsal arista. The 
wings are usually large but may be small or entirely ivanting. There 
are two strong veins extending half way to the apex of the wing, and several 
weaker ones running obliquely across the wing. The larvae usually live on 
decaying vegetation or animal matter ; some live in ants nests. 

Aphiochaeta ferruginea, Brunetti. Female. Head brownish yellow, 
tinged with grey ; antennae pale yellow, third joint large as in most of 
the members of the Phoridae ; arista long and minutely pubescent. 
The frons has four rows of four bristles. Thorax bright ferruginous 
or brownish yellow. Abdomen dark ferruginous or brownish yellow ; 
sometimes it is blackish with a red tinge, altering the general appearance 
of the fly. It is widely distributed, and has been recorded from most 
parts of India, Ceylon, Burma, Malay, West Indies and Central 
America. 



APHIOCHAETA FERRUGINEA 



307 



Its larva is of a yellowish colour ; the anterior extremity is pointed, the 
posterior end is bluntly rounded off, and armed with a number of short 
stiff spines. The pupa, according to Austen, is buff-coloured, and of the 
usual boat-shape characteristic of the family ; the anterior end at first 
tapers and then becomes abruptly truncated. The posterior extremity is 
blunt and has a row of minute spines. 

This is one of the most important phorids, as it infests the human 
intestinal canal in its larval stage. Brunetti states this fly was originally 
sent to the Indian Museum in 1891 by Crombie with a note that it 
was, ' reared from eggs passed in the excrement of a European in 
Rangoon, eggs, grubs and flies all being voided together '. 

Austen, in a paper on ' Some Dipterous Insects which cause Myiasis in 
Man ', records some observations made by Baker which suggest that 
A. ferniginea is capable of living in the human intestine, and laying 
its eggs, so that the patient passes out larvae, pupae and mature 
flies. This is a remarkable life history, and one which, at first 
sight, would seem to be impossible. Austen, however, points out that 
another phorid belonging to the genus Conicera has been found in 
America in a human body exumed two years after burial, and that 
living larvae, pupae and adult flies were found together. 

Recently some specimens of larvae of A. ferniginea from the faeces 
of a European at Negri Sembilan, in the Federated Malay States 
were sent by Mr. Jackson to the King Institute for identification ; here, 
however, there were no adult flies seen in the faeces. The result of the 
invasion of the human intestine by the larvae of this fly is that they may 
continue to be passed out for as long as a year, with symptoms 
simulating those of beri beri. Aphiochaeta ferniginea may also cause 
cutaneous myiasis ; Austen records an instance of this from British 
Honduras. 

FAMILY ASILIDAE 

Small or large to very large flies, always elongate and with spiny 
legs. The head is broad and short, and nearly always flattened and 
jointed to the thorax by a well marked flexible neck ; both sexes are 
dichoptic. 

1 These flies have been aptly named ' Robber flies ' on account of their 
piredaceous habits ; they are often to be seen resting motionless on walls, 
stones, railings, etc., watching for their prey, which is always some 
insect, often a fly. They dart with great suddenness and grasp their 



308 



MEDICAL ENTOMOLOGY 



prey with their legs and impale it with their proboscides, usually in the 
region of the neck. They then return to some perch and suck out its 
body juices. 

In Madras a small species regularly preys on Philaematomyia insignis, 
when it is laying its eggs in cow dung. 

Kershaw has recently described the egg laying habits of a species of 
asilid {Promachus) from the Kwantung Province of South China. The 
female, lays her eggs, about fifty in number, in a mass on long coarse 
grass stalks, the bare ends of twigs, etc., about two or three feet above 
ground ; she covers them with a thick gelatinous substance like that used 
by some tabanids. The larvae hatch out in six or seven days, drop to 
the ground and at once burrow into the earth ; it is not known exactly on 
what they feed, but Kershaw thinks they live on subterranean coleopterous 
larvae. 



CHAPTER IV 



SECTION 1 

THE ORDER DIPTERA: THE CYCLORRHAPHA 

The suborder Cyclorrhapha is divided into two primary divisions, the 
Aschiza and the Schizophora, as pointed out in the previous chapter. 
In the Aschiza are included those forms in which the frontal lunule is 
indistinctly seen above the base of the antennae, while the frontal suture 
is entirely absent ; the third antennal segment is always simple, and has 
either a terminal or a dorsal arista ; the third vein is never forked, and 
there are never more than three complete posterior cells. The em- 
podium is never pulvilliform. 

In the Schizophora the frontal lunule is distinct and the frontal 
suture always present ; none of the longitudinal veins are forked, and 
there are never more than three posterior cells present. The antenna 
is three-jointed and always simple ; the arista is usually plumose and 
placed dorsally ; most of the species are bristly insects. This group is 
further divided into the Acalypterae and the Calypterae. In the former 
the squamae are small, sometimes even rudimentary ; the thorax is with- 
out a complete suture, and the auxiliary vein is often small or vestigial. 
In the Calypterae the squamae are well developed ; the thorax has a 
complete suture, and the auxiliary vein is always well formed throughout 
its course. 

Altogether there are about thirty families included in the suborder 
Cyclorrhapha, three of which, the Syrphidae, Pipunculidae and Platype- 
zidae, are placed in the division Aschiza ; as none of the species contain- 
ed in these families are of any interest to the worker they will not be 
referred to again. In the group Acalypterae of the Schizophora there 
are no blood-sucking forms, but many of the species are of interest 
on account of the natural parasites they may harbour; the families con- 
taining these species are dealt with below. All the blood-sucking 
Cyclorrhaphic Diptera, and those forms which are of special isiterest on 
account of their domestic habits, are confined to the Calypterae, 



310 



MEDICAL ENTOMOLOGY 



THE ACALYPTERAE 
FAMILY SEPSIDAE 

Small ant-like flies of a black or amber colour. Head globular in 
shape; proboscis and antennae short. Abdomen slender and narrowed 
at the base ; male genitalia prominent. Subcostal or auxiliary vein dis- 
tinct or united to the first vein ; anal and basal cells distinct. 

The Sepsidae are commonly seen in the tropics on dung of all kinds ; 
at first sight they may be mistaken for winged ants on account of their 
characteristic shape, the abdomen being narrowed at the base. In 
India they are extremely common on cow dung and may often be seen 
in swarms dancing and flitting about on its surface ; their irridescent 
wings and the quaint attitudes they assume make them very striking 
objects. Their larvae can, as a rule, be recovered in large numbers from 
the dung on which the flies are feeding, and may be recognized by the 
presence of two prominent spines at the posterior end. If disturbed they 
have the habit of inserting their mouth parts into notches on the last 
segment, and by suddenly releasing them propel themselves four or five 
inches. 

In Madras two species of Sepsis are infected with flagellates, one with 
a herpetomonas and crithidia, and the other with the crithidia alone ; in 
the Soudan, Roubaud has found another species infected with a herpeto- 
monas. It is interesting, in view of recent controversies, to note the 
presence of a true crithidia in a purely dung-feeding insect. 

FAMILY CORDYLURIDAE 

Medium-sized grey to black flies. Head globular ; both sexes dichoptic. 
Wings large ; auxiliary vein always distinct, basal cells large and 
complete. Squamae small, with the upper one concealing the lower. 
Abdomen with more than four visible segments. 

Cord}lurids are common about decaying vegetable and animal matter, 
and especially near foul water ; many of the species of Scatophaga may be 
seen on cow dung. The species are of practical interest in that they 
may be infected with flagellates of the genus Herpetomonas. The 
Cordyluridae may be distinguished from the Anthomyidae, many of which 
have the same habits, by noting that the squamae are always small in 
the former and the male eyes are widely separated ; in the latter the 
squamae are large and the male eyes are much closer together. 



FAMILY DROSOPHILIDAE 



311 



Mackinnon has recorded Herpetomonas miiscae domesticae, Burnett, 
from Scatophaga littaria in England ; in this case the parasite was 
found in the larvae as well as in the imagines. 

FAMILY BO'RBORIDAE 

Small to very small brown to black flies. Head hemispherical ; antenna 
short with the third joint rounded ; arista bare or pubescent. Subcostal 
vein wanting or if present indistinct. Legs long and well developed ; 
hind metatarsi dilated and shorter than the next joint. 

This family contains, in addition to others, the two genera Borborus 
and Sphaerocera , the species of which may be seen in swarms about 
dung and other refuse. In Madras, a small Borborus, which is very 
common on cow dung, is nearly always infected with a species of 
herpetomonas. According to Chatton, Sphaerocera subsultans in France 
is infected with a species of herpetomonas, H. legerorum. Another 
borborid belonging to the genus Limosina, L. hirtula, is also infected 
with a similar flagellate. 

All the above dung flies can be bred out by collecting their larvae and 
placing them in some fresh dung in a large tray ; when about to pupate 
the larvae as a rule do not migrate, so that the pupae 
are found in the dung. If cow dung is collected in a technique 
heap under a tree and regularly replenished large numbers of sepsids 
and borborids will soon collect on it, and their larvae can be obtained 
in a few days. The pupae should be placed in a breeding jar, such 
as that described further on in connection with the breeding of the 
Muscidae ; when the flies hatch out they may be fed on fresh cow dung ; 
the larvae, as well as the imagines, should be examined for flagellates. 

FAMILY DROSOPHILIDAE 

Small stumpy flies usually with characteristic red eyes. Antenna with 
the third joint oval ; arista plumose with long but scanty hairs. 
Abdomen short. Subcostal vein absent or indistinct ; first longitudinal 
vein short ; basal and anal cells not distinct. 

The Drosophilidae are also of interest on account of the natural flagel- 
lates which some species may harbour. In all parts of the world they are 
common about fruit, and the fermenting refuse which collects around 
wine vats. Though popularly spoken of as Fruit Flies, the Drosophilidae 
should not be confused with the Trypetidae, the well-known fruit 



312 



MEDICAL ENTOMOLOGY 



pests. Hewlett records a species of Drosophila from Northern India 
which completes its whole life histor}- within a week ; this is, as he points 
out, the shortest life history yet recorded for an insect with a complete 
metamorphosis. 

In Madras there are two species which are commonly seen hovering 
about ripe fruit, especially during the rainy season ; both are infected 
with a species of herpetomonas. In France another species, Drosophila 
confiisa, is commonly infected with Crithidia drosopliilae, Chatton and 
Alilaire. 

In order to breed these flies it is only necessary to place some bananas 
in a tray, and allow them to become over-ripe ; the flies will soon collect 
on them in large numbers and deposit their eggs, which are very small 
and have two long filamentous processes. If the fruit is not disturbed 
the pupae will be found in large numbers collected on the outside of 
the bananas, and along the sides of the tray. As in the case of 
the dung flies the pupae should be placed in the breeding jar and the 
imagines fed on fruit ; the larvae should always be examined for the 
flagellates. 

THE CALYPTERAE 
FAMILY ANTHOMYIDAE 

Small to medium-sized flies in general appearance resembling those of 
the genus Musca ; greyish or brownish black in colour, rarely metallic. 
Male less dichoptic than the female. Antenna of the muscid type ; 
arista either plumose or bare. First posterior cell widely open. 
Abdomen composed of four or five visible segments, rarely armed with 
bristles. Squamae well developed. 

This family contains the genus Homalomyia (Fannia), the species of 
which have domestic habits and regularly enter human habitations. 
H. canicularis is the best-known example, and is popularly spoken of as 
the ' Lesser house fly ' ; its larvae have been recorded from the human 
intestine. The larvae of the majority of the Anthomyidae are vegetable 
feeders, and many are destructive to garden produce. Others again 
breed in dung and the decomposing bodies of animals ; these forms are 
usually infected with natural flagellates. Mackinnon records Herpetomo- 
nas muscce domesticae from the larva of Homalomyia corvina from cow 
dung. In Madras there are several of these dung-frequenting antho- 
myids which are also infected with flagellates ; one in particular can be 
caught in large numbers by placing some decomposing meat in the open. 



SARCOPHAGIDAE OR FLESH FLIES 313 



FAMILY TACHINIDAE 

Small to large, bristly flies with thick-set bodies. Antenna of the 
muscid type; arista entirely bare. Proboscis either short or long. 
Abdomen composed of four or five visible segments armed icith lateral 
and terminal bristles. First posterior cell either narrowed or closed. 
Squamae ivell developed. Larvae parasites of other insects. Adult flies 
flower feeders. 

At the present time this family contains nearly 200 genera, about 180 
of which are found in North America ; many of them bear a superficial 
resemblance to the Sarcophagidae (see below), but can be distinguished by 
the bare arista, the well-developed squamae and the closed or narrowed 
first posterior cell. The mature insects live on the juices of plants and 
flowers, and are usually found in places frequented by the hosts which 
the}' parasitize. The larvae of the Hj-menoptera and Lepidoptera are 
their usual hosts, but some parasitize those of the Coleoptera, Orthoptera, 
Hemiptera and even Diptera. In America their breeding habits have 
been carefully studied, and several species have been used in checking 
other injurious insects, particularly certain species of moth, but it must 
be admitted with very little success. The various methods employed by 
the female flies in parasitizing their hosts are described in the case of 
several species by Townsend in a paper entitled, ' A record of results 
from rearing and dissections of Tachinidae ' ; the worker who is interested 
in this subject should consult this valuable paper. 

FAMILY SARCOPHAGIDAE 

Medium-sized to large thick-set flies. Front broad in the female, 
somewhat narrower in the male. Arista plumose to the middle or a 
little beyond it, the distal portion bare. Abdomen composed of four 
visible segments ; bristles as a rule confined to the distal portion, but 
sometimes present on the margins of the second and third segments. First 
posterior cell narrowed or closed. External genitalia of male prominent. 

The Sarcophagidae, or ' Flesh flies ' as they are commonly called, may 
be seen about decaying animal and vegetable matter ; in India they fre- 
quent latrines and night soil trenches. Although the family' contains 
only a few genera, the species are numerous and verv difficult to distin- 
guish. Their larvae feed on animal and vegetable matter, or live as para- 
sites in sores, causing dermal myiasis, and in the nasal cavities of man 
and animals. In Gujarat it is not uncommon to see large sores on the 

40 



314 



MEDICAL ENTOMOLOGY 



scalp full of the larvae of a species of Sarcophaga. A case of nasal 
myiasis, in which numbers of the larvae of a species of Sarcophaga were 
recovered by nasal douching, has been recorded by Patterson from Assam. 
As so little is known regarding this habit among the Sarcophagidae it is 
not possible to say whether it is one of the regular methods of reproduc- 
tion or not. In Madras the larvae of several species are found in human 
faeces and in the dead bodies of animals ; in the tropics food of this 
nature is abundant everywhere. 

The flies of the genus Sarcophaga are larviparous, and F"abre, in his 
delightful account of the habits of the Blow Fly {Calliphora erythroce- 
phala), points out that the female S. cariiaria will deposit her larvae 
on a piece of meat from a height of twenty-six inches, thus showing that 
the common wire dish cover or meat safe affords little or no protection, 
for she can drop her larvae through the meshes. 

The larva of Sarcophaga is amphineustic, pointed anteriorh' and round- 
ed posteriorly ; the segments are differentiated b^- large transverse swell- 
ings, each provided with a circlet of spines. The posterior stigmata 
are concealed in a depression in the last segment, and there are promi- 
nent bifid anal swellings. The puparium is reddish brown and ovoid in 
shape. 

A large species of Sarcophaga in Madras is nearly always infected 
with Herpefonionas sarcophagae, Prowazek ; according to Roubaud Sar- 
cophaga mints in the Congo is infected with Herpetonionas muscae 
domesticae, and Swingle has recorded another species of herpetonionas, 
H. Jineata, from Scrcophaga sarraceiiiae in North America. 

In order to breed these flies for experimental purposes some decompos- 
ing meat should be placed in a tray in the open : the female Sarcophaga 

is attracted to it, and when the larvae are deposited the 
Breeding Technique , t,. 

meat should be placed m a mud enclosure (rlate XLlx , 

fig. 5) made as follows : — Mud and cow dung are mixed together and 

made into a walled enclosure one foot square and eight inches high; while 

the mud is still moist a board is accurately fitted as a cover on the top, in 

order to keep out stray flies. The mud is allowed to dry until it becomes 

quite hard, and the enclosure is then ready for use. It should be built 

on to a table so that it can be protected from ants. The meat containing 

the larvae is placed in a small tin tray, which is then laid on sand at the 

bottom of the enclosure. Such an enclosure can be made b)- most 

natives, and is useful for breeding Muscidae. If the meat is left 

in a tray containing some sand on a table in the laboratory the larvae 

will crawl out of it when they migrate in order to pupate, and will 



FAMILY OESTRIDAE : CLASSIFICATION 



315 



be found scattered all over the floor of the laboratory. These larvae will 
even crawl out of a large glass jar. From experience it has been found 
that the)- never leave the mud enclosure, but ah\ays pupate in the sand. 
This enclosure has the further advantage of minimizing the smell from 
the decaying meat ; if the latter is left in a tray or glass jar it becomes 
unbearable. The enclosure will be referred to again in connection 
with the breeding of Miisca. 

FAMILY OESTRIDAE 

Medium to large flies icifh thick-set bodies, large heads and rudiment- 
ary mouth parts. Antenna short, three-jointed and hidden from view in 
the facial groove. Front wide in both sexes; eyes comparatively small. 
The thorax has a distinct transverse suture ; the squamae are as a rule 
large, hut may be small. Wing venation of the muscid type; the first 
posterior cell is either narrowly open or entirely closed. 

This family consists of a comparatively small group of flies of the ut- 
most importance to the veterinarian, and of the greatest interest to the 
dipterologist. They are popularly known as ' Bot flies ', ' Warble flies ', 
or ' Breeze flies '. The mature insects are as a rule found either in the 
open country resting on leaves, or on the ground along roads and path- 
ways frequented by the hosts which they parasitize. 

The great economic importance of the Oestridae has long been recog- 
nized, and it is not, therefore, surprising to find that their life histories 
were known to Linnaeus and many of the older entomologists. The best 
modern account of this family is that of Brauer, who unquestionably had 
the most profound grasp of the subject ; his monograph is still the 
standard work on the structure and life histories of the Oestridae. 

Numerous attempts have been made to classify the Oestridae, first ac- 
cording to the structure of the larvae, and secondly according to their 

habits. They were formerly divided into two groups, 
, 1111 1 111 11 Classification of 

those m which the larvae have oral hooks, and those Oestridae 

without external mouth parts. Brauer points out that 

though this grouping is useful in distinguishing the full-grown larvae, it 

is incorrect, as all oestrid larvae have oral hooks when very young. It is 

also an unnatural classification, as no relationships exist between the two 

types of full-grown larvae and the perfect insects. 

Clark suggested the second method of grouping the lar\-ae, viz., to 

arrange them according to their habits, into cavicolae, cuticolae and 

gastricolae, but Brauer points out that this classification is also 



316 



MEDICAL ENTOMOLOGY 



inadequate, for while the species of a genus may agree in their parasitic 
hfe histories, the larvae of different genera may have the same 
habits. He instances the habits of the larvae of Hypodenna, Ciiterebra, 
Dermatobia and Cepheiiomyia, and points out that there is far more 
difference between the mature insects of one and two, than between two 
and three. The larvae of Cepheiiomyia live, as a rule, in the oesophagus, 
the Oestrus larvae in the frontal and nasal cavities, the Gastrophilus 
larvae in the intestinal tract, and those of Hypodenna in the subcutan- 
eous cellular tissues. 

The adult flies have been grouped according to the structure of the 
antennal bristles, into those in which they are pectinate {Ciiterebra 
and Dermatobia), and those in which the bristles are naked {Hypodenna, 
Gastrophilus, Cepheiiomyia, Cephalomyia) ; the larvae of the former are 
found in the bodies of Rodents and Marsupials, and in Ungulates ; 
those of the latter only in Ungulates. These groups are, however, un- 
natural, for the larvae of Oestrus leporinus, which has naked bristles, is 
parasitic in a rodent, as its name implies. Brauer considers it best to 
classify the larvae according to their genera, for those of each genus have 
a similar life history. . The generic characters of the imago always 
afford a reliable clue to the probable life history of an unknown larva ; 
in the case of new genera experience is the best guide in predicting the 
probable life history of the larva. 

Williston's Key to the Genera of the Oestridae. 
Imagines. 

1. Mouth parts very small, vestigial ; arista bare ...... 2 

Proboscis geniculate, inserted in a deep slit ; female without 

extricate o\-ipositor ; first posterior cell narrowed or closed ; 
arista bare or plumose ; facial grooves approximated below, 
enclosing a narrow median groove or depressed surface ; 

squamae large ........ ... 6 

2. The fourth longitudinal vein runs straight toward the border 

of the wing, i.e., the apical cross-vein is obsolete, and the 
first posterior cell is narrowed ; squamae small ; female ovi- 
positor elongate ; larvae in stomach and intestinal canal . Gastrophilus. 
The fourth vein turns forward to form the apical cross-vein, 

closing or narrowing the first posterior cell ... ... 3 

3. Facial grooves approximated below, leaving a narrow median 

groove or depression ........ ... 4 

Facial grooves remote, enclosing between them a broad, gent- 
ly arcuate, shield-shaped surface ; squamae large ; female 

with elongate ovipositor ; larvae hypodermatic ... ... 5 

4. First posterior cell closed and petiolate ; body nearly bare . Oestrus. 
First posterior cell narrowly open ; body pilose . . . Cephenomyia. 



OESTRID LARVAE 



317 



Palpi wanting Hypoderma. 

Palpi small, globular Oedamagena. 



6. Arista bare, short and stout ; wings without stump at angle of 

fourth vein ....... 

Arista pectinate above ..... 

7. Tarsi broad and flattened, hirsute ; alulae large 
Tarsi slender, not hirsute ; third joint of antennae more 

elongate ; front prominent anteriorly ; alulae of moderate 
size ........... 



Bogeria. 
Cuterebra. 



Dermatobia. 

The body of the Oestrid larva is composed of tw elve segments, the 
lirst two of which cannot be differentiated from the cephalic ring ; no 
head can be recognized. The anterior stigmata ap- 
pear as small knobs or fissures and are partially hid- Structure^of Oestrid 
den in the folds of skin (Gastrophihis). The posterior 
stigmata may be protrusile or retractile. In the mature Gastrophihis 
larva and in that of Dermatobia they are protected by lip-like organs on 
the last abdominal ring ; in all the other genera they can be simply 
withdrawn into the preceding ring ; they consist of chitinous, cresentic or 
reniform plates. 

All the young larvae have mouth parts ; in the later stages some have 
oral hooks while others have none. In Hypoderma the appearance 
changes after the first moult and the oral hooks and mouth parts 
disappear. The antennae are rudimentary, consisting of membraneous 
papillae. The anus is small, and is situated between the stigmal plates. 
The larvae moult twice during the parasitic period. In the third stage 
they reach their full size, change in colour, and are then ready to leave 
their hosts ; those living in the skin drop out and pupate in the ground, 
while those in the various internal organs are either passed out or crawl 
out in order to pupate. They all feed on the juices of the host, or on 
the exudation which surrounds them. 

Williston's Key to the Oestrid Larvae 

1. Last abdominal segment free, broadly attached ...... 2 

Last abdominal segment (twelfth) retractile within the preced- 
ing, small and distinctly constricted ........ 7 

2. Larvae with two pairs of chitinized jaws ; that is with two 

outer mouth-hooklets, and two inner, straight, triangular 

points (Horses) Gastrophihis. 

Larvae with two or no mouth booklets ......... 3 

3. Larvae on the median segments with dorsal, spindle-shaped 

tubercles ; one pair of mouth booklets present ...... 4 

Larvae without such tubercles ; one pair or no mouth booklets 

present ............. 5 

4. Antennae broadly separated ; body oval, strongly convex 

above, flat below (Sheep) ... ... Oestrus. 



318 



MEDICAL ENTOMOLOGY 



Antennae approximated or contiguous ; body elongated, some- 
what broader in front than behind (Deer) .... Cephenomyia. 

5. No mouth booklets ............ 6 

Two small mouth booklets present (Rodents) .... Oestromyia. 

6. Bristly covering alike above and below (Reindeer) . . . Oedamagena. 
Bristles stronger below than above (O.x, etc.) .... Hypoderma. 

7. Larvae oval (Rodents, Marsupials) ...... Cuterebra. 

Larvae club-shaped, more slender posteriorly (Artiodactyls, 

Carnivora, Primates) Dermatobia. 

Genus Gastrophilus, Leach 

This genus, the main characteristics of which are given in the above 
keys, contains some fourteen species distributed all over the world. Those 
larvae which are known live in the stomach and intestines of Equines ; 
the adults are known popularly as ' Bot flies '. Garman gives the follow- 
ing key for the identification of the common species : — 

Key to the Common Species of Gastrophilus. 



1. Discoidal cell closed by cross-vein ......... 2 

Discoidal cell open pecorum. 

2. Wings marked with brown ....... equi. 

Wings not marked with brown ......... 3 

3. Anterior basal cell nearly, or quite, equal to the discoidal cell 

in length nasalis. 

Anterior basal cell markedly shorter than the discoidal cell haemorrhoidalis. 



Gastrophilus equi, Fabr., the bot fly of the horse, is the commonest 
species, and has long been familiar to farmers and veterinarians. The 
fly is of a brownish colour with rows of black spots on the lower borders 
of the abdominal segments ; the wings are pale with dark transverse bands 
about the centre. When about to oviposit the female fly hovers near a 
horse with its body bent downwards and the ovipositor fully extended ; 
it then darts suddenly on to the skin and glues an egg lightly on to the 
end of a hair, and then rapidly retreats to hover again until the next egg 
is ready to be laid. The egg is pointed at the lower end, while the 
upper has a well marked operculum. Osbourne, who has studied the 
conditions under which the eggs hatch, has found that they require some 
friction and moisture to enable them to do so, and that this is sup- 
plied by the horse licking its skin, or that of another horse. Hatching 
sometimes takes place before the tenth day after the eggs are laid, but 
more usually after the fourteenth day. This knowledge is of importance 
for it enables the horse keeper to know within what period he should 
destroy the eggs. 



GENUS HYPODERMA 



319 



Gastrophilits haeiuon'hoidalis, L., the red-tailed hot Hy, is another 
species the larvae of which are parasitic in the stomach of the horse. 
It is a small fly and can be recognized by the orange red tip of the 
abdomen ; it oviposits on the nose and lips of the horse. Its eggs are of 
a dark colour, and at the time they are laid contain nearly developed 
embrj-os, so that they hatch out much more quickly than those of eqiii. 

Gastrophilits nasalis, L., the ' Chin fly ' has much the same habits 
as the former species, depositing its eggs on the lips and margins of the 
nostrils of the horse. 

Genus Oestrus, L. 

This genus contains the well known Oesfnis ovis, L., the bot fly 
or head maggot of the sheep, known to man from ancient times. It 
deposits its larvae in the nostrils of sheep, from which they migrate into 
the frontal sinuses, causing much discomfort to the animal ; when in 
large numbers they have been known to cause the death of the host. The 
larvae attach themselves by their hooks to the membraneous lining 
of the cavities and feed on the secretion which surrounds them ; 
when about to pupate they either crawl out of the nasal chambers 
or may be sneezed out. The pupal stage lasts about two months. 
The fly is found almost throughout the world. 

Genus Hypoderma, Latrielle 

The oestrids belonging to this genus are commonly known in 
America as ' Warble flies ', or ' Heel flies '; they are characterized by the 
complete absence of palpi ; their larvae are parasites of the hides of 
cattle, and as such cause great loss to farmers. In a recent paper on 
Warble flies from Canada, Hadwen points out that the average percent- 
age of infected hides (' grubby hides ') in the provinces of New 
Brunswick, Quebec, Ontario, and British Columbia amounts to 
32'22 per cent. This loss falls mainly on the farmer, for warbled hides 
are of little or no value. 

The warble season in Canada, from the tanner's point of view, extends 
from late January to early July, the worst period being during the month 
of April. Hadwen found that the first larvae of Hypoderma hovis, 
de Geer, emerged from the skins on April 10th, and the last about 
July 2nd. The larvae were most prominent in the hides about April 
10th, and had perforated the skin some time before. Hadwen states that 
all tanners are agreed that rough, long-haired, ill-kept animals are those 
which are chiefly attacked ; well-kept, sleek animals are rarely parasitised. 



320 



MEDICAL ENTOMOLOGY 



He thinks that this is mainly due to the fact that weakly animals cannot 
escape the attacks of the flies, whereas well-cared for animals resent 
their attentions and usually run away ; such animals are usually kept in 
stalls during the heat of the day when the imagines are most in evidence. 
Warbles are less common during wet and cold weather. 

Up to the time of the publication of Hadwen's paper, it was believed 
that Hypoderma lineata, Villers, was the common Warble fly of North 
America ; it would now appear that this is not the case, Hypoderma 
hovis being the common species. 

Hypoderma bovis, de Geer, is about half an inch long and in general 
appearance simulates a honej' bee ; it is a very hairy insect. On the front 
part of the thorax the hairs are yellow, in the middle they are black and 
shiny, while on the posterior part they are whitish. On the base of the 
abdomen the hairs are whitish yellow, in the middle portion they are 
dark, and at the apex orange red. 

Hypoderma lineata, \'illers, another North American species, is about 
the same size as boi'is. The hairs on the thorax are yellowish white, 
reddish and brownish black ; in addition there are four narrow light 
longitudinal lines on the thorax from which it gets its name lineata 
a white horizontal band runs across the posterior end of the thorax. 
The hairs of the terminal segment of the abdomen are lemon yellow 
in colour. 

The egg of Hypoderma bovis is about 1 mm. long and is of a }'ellowish 

white colour. It consists of two distinct parts, the egg itself and the 

pedicel or clasping base ; the latter consists of two lips. 

Early stages. According to Hadwen, who has studied the egg and 
The egg. ° .... 

the method hy which it is laid, the pedicel end comes 

out of the ovipositor first ; in some way or other the lips are opened and 
adapted to the hair close to its root, the sticky substance accompanying 
the eggs causing them to adhere to the hairs. This method of oviposition 
is in marked contrast to that in Gastrophiliis, in which the egg is lightly 
fixed to the end of a hair. The eggs of Hypoderma are laid singl}'. 
Hadwen shows that the favourite sites for the fly to lay her eggs are 
in the region of the hock, the back of the knee and occasional!)' as 
high as the stifle and along the flanks. Rarely the fl}' will lay an egg 
near the jaw. 

When about to oviposit the fl}' strikes the animal in a clumsy manner — 
it never planes over it as has been described by several authors — settling 
for a moment while it glues on its egg at the root of the hair. It is the 
pertinaceous way in which it repeats the process, buzzing round and 



BOT FLIES OF ANIMALS 



321 



striking, which makes the animal frenzied with fear and causes it to 
run away. 

As already stated the third and last stage of the larva of Hypoderma 
bovis is found in the skin of the backs of cattle. Exactly how it 

reaches this situation is not clear : one thing, however, is 

111 1 1 1 , • T**^ ^^""^^ 

certam, that the larvae do not burrow into the skm on 

hatching out of the eggs. It is at present believed that they are licked 
off from the skin or hairs and then make their way into the mucous 
membrane of the oesophagus, where they are found in their first stage. 
These larvae measure about 3"5 to 11'5 mm., and are armed with minute, 
almost invisible, rows of spines on all the segments. When this stage is 
completed, after about five months, the larva burrows through the muscles 
and eventually reaches the skin of the back, where it passes its third 
stage ; just before leaving the skin to pupate it measures about 22 mm. 
in length. The larva of Uneata has many spines on the dorsal and 
ventral surface of the penultimate segment, \\hile in that of bovis there 
are no spines. 

Hadwen adopted the following method of securing the larvae when 
they were about to leave the skin to pupate : — A piece of gauze is 
glued over the warble ; some powdered aloes is mixed with the glue and 
a little dusted over the patch to prevent the cattle from licking the sores. 
The larvae will be found under the gauze, or on the floor of the stable, 
always in the morning. The pupal stage lasts from thirty to forty days. 

Several bots belonging to allied genera live in the nasal cavities of 
animals. For instance, one species of Cephalomyia, Macq., (C. maciilafa,) 
is found in the throat and nasal cavities of the camel 
and buffalo in India ; one species of Rhinoestnis, Brauer, ^^J^ 
{R. purpureus) lives in the nasal cavities of the horse ; 
another R. hippopotami, Griinberg, in the nasal cavities of the hippo- 
potamus ; the larvae of the single species of Pharyngoboliis, Brauer, 
(P. africanits) lives in the nasal cavities of the elephant, but the imago is 
unknown. The larva of the only species of Pharyngomyia, Schiner, 
(P. picta) lives in the pharynx of Cerviis elephas, and is found through- 
out Europe. Seven species of the genus Cephenomyia live in the 
pharyngeal cavities of various kinds of deer in Europe and America. 

Many rodents in America are attacked by the larvae of hot flies belong- 
ing to the genus Ciiterebra, Clark. The common species is C. emasciilator, 
Fitch, the ' Emasculating hot fly ', so called on account of the habitat 
of its larvae which live in the scrotum of squirrels and chipmunks. The 
rabbit is also attacked by another species, C. cuniculi, Clark, which 
41 



322 



MEDICAL ENTOMOLOGY 



in its larval stage is found under the skin of the rabbit, causing a 
large tumour. 

Genus Dermatobia, Brauer 

The main characters of this genus are summarized in the above key; it 
contains one species Dermatobia cyaiiiventris, Macq. (syn. iioxialis, 
Goudot). 

Dermatobia cyaniveiifris. Head when viewed from above triangular in 
shape with the apex directed towards the frontal lunule. Thorax 
metallic blue, about as broad as it is long, with a dark median stripe, 
narrowest in front of the transverse suture and broadening out 
behind it ; in addition there are two dark admedian stripes converging 
anteriorly towards the median stripe, which they join. There is also 
a dark curved band situated on each shoulder and a broader one at the 
sides. Abdomen ovoid, consisting of four visible segments of a metallic 
blue colour. Length 12 mm. 

This fly is common in South America, where it is known as ' Verma- 
caque ' ; it normally causes cutaneous mj'iasis in animals, chiefly cattle 
and equines ; occasionally it attacks man. The larva is of a characteris- 
tic shape, narrow and tubular at its posterior end, flask-shaped at its 
anterior extremity. The eggs are laid on the skin and the larvae burrow 
into the cellular tissue, where they form a large tumour. 

FAMILY MUSCIDAE 

Small to large flies either of a bright metallic colour without thoracic 
markings, or greyish black with thoracic bands ; they may be either 
bare or sparsely covered with hairs; never bristly and rarely elongate. 
The arista is as a rule plumose on both sides and nearly always to the 
extremity. The eyes, which are nearly always bare, are more or less conti- 
guous in the male ; in the female they are xcidely separtaed. Proboscis 
either long, directed forwards and armed for biting, or folded back and not 
armed for biting. Abdomen composed of four or more visible segments, 
the first fused with the second. Venation characteristic ; first posterior 
cell closed or nearly so, except in the blood -sucking genera, in ivhich it is 
open to a considerable extent; in the Glossininae the wing venation 
has undergone a remarkable reduction. The male genitalia are as a rule 
not prominent. 

The blood-sucking members of the Cyclorrhapha are confined to 
the Muscidae. In this family there are two notorious insect pests, 



FAMILY MUSCIDAE 



323 



the house fly, Miisca domestica, L., and the tsetse fly, Glossina palpalis, 
R-D. ; the former insect, in addition to causing great annoyance, is 
able to contaminate food with pathogenic bacteria, and it has followed 
man in his migrations all over the globe ; the latter transmits the 
parasite of Sleeping Sickness, but is fortunately localized in its distribu- 
tion. The Muscidae also include several veritable pests of the domesti- 
cated animals, some of which carry dangerous parasites. Any one 
who has observed a horse or a cow being attacked by hundreds of blood- 
sucking muscids, such as Stomoxys, Lyperosia and Philaematomyia , will 
realize the extent to which these animals are worried by such insects. 

Although man is not usually troubled by these smaller blood-sucking 
muscids, there are others, the Calliphorinae, which have the habit of 
depositing their eggs or larvae in his subcutaneous tissues or nostrils. 

The Muscidae which concern the worker may be grouped as follows ; it 
should be understood, however, that this table is not meant to define 
their exact genealogy, but rather to indicate their probable relationships. 

MYODARIA, R-D [MUSCIDAE (sen. lato.) of authors] 




MUSCOIDEA 



ANTHOMYIOIDEA 



MUSCIDAE (sen. restrict.) 



CALLIPHO- MUSCINAE PHILAEMA- STOMOXYDINAE GLOS- 
RINAE TOMYINAE SININAE 



Calliphora 

LUCILIA 

Pycnosoma 

Chrysomyia 

auchmeromyia 

Choeromyia 

ochromyia 

Bengalia 

cordylobia 



Muse A 



Philaema- 
tomyia 



Stomoxys Glossina 

Haematobia 

Bdellolarynx 

Haematobosca 

Stygeromyia 

Lyperosia 



324 



MEDICAL ENTOMOLOGY 



THE CALLIPHORINAE 

Medium-sized to large flies, usually of a bright metallic colour, but 
sometimes yellowish. Eyes bare or pubescent ; cheeks bare or hairy. 
Arista usually plumose up to the tip, rarely bare, but sometimes pectinate. 
Front in male as a rule narrow, sometimes wide, as in Auchmeromyia 
and Bengalia. Thorax of a uniform colour usually without stripes or 
bands ; either with or without tomentum between the bristles. Posterior 
dorsocentral and acrostichal bristles well developed and as a rule con- 
stant, but the former may be unequally developed. Sternopleural bristles 
varying in number and arranged either 0:1 ; 1:1 or 2 : 1 .* Abdomen 
round or ovoid, rarely elongate. Venation of the muscid type; bend 
of fourth vein either angular or rounded. 

In this subfamily there are about twenty genera and at least 200 
species. Although none of the imagines are true blood-suckers, many 
of them frequent food, particularly meat when exposed for sale, and in 
this way they may be found to contain blood. At least one of the 
species belonging to the genus Ochromyia is predaceous in its imago stage, 
feeding on ants ; this habit appears to be the exception rather than the 
rule in the Calliphorinae. There are, however, several grades of parasitism 
exhibited by the larvae of the Calliphorinae. As far as is known at 
present, all the species are oviparous, and as a rule the females deposit 
their eggs in decaying organic matter ; in the majority of instances they 
prefer the dead body of some animal to any other situation in which to 
deposit their eggs. Some of the flies, however, will readily lay their eggs 
in sores and injuries on the skins of sickly animals; the larvae live on the 
juices surrounding them. There are several species of Lucilia which 
occasionally exhibit this habit and cause cutaneous myiasis. On the other 
hand, there are many species belonging to several genera in which this is 
the regular habit ; the females are attracted by any offensive smell and even 
by shed blood, and will deposit their eggs in the skin and nostrils of man 
and animals. The last grade of parasitism, and the one which Townsend 
considers to be of recent origin, is well exemplified by the species of the 
genus Auchmeromyia and Choeromyia ; their larvae are true blood- 
suckers and bite man and animals. 

* This method of denoting the arrangement and position of the sternopleural bristles is 
commonly used by Dipterologists ; 0 : 1 indicates that the anterior bristle is wanting and that 
there is one posterior bristle, and so on. 



BLQW FLIES. 



325 



Genus Calliphora, Robineau-Desvoidy 

Meditun-sized to large flies usually of a metallic colour. Posterior 
dorsocentral and acrostichal bristles constant and well developed. Sterno- 
pleural bristles arranged 2:1. Prothoracic stigmata brownish red. 
Base of third longitudinal vein spinulose. 

, This genus contains the ' Blue Bottles ', or ' Blow flies ', insects which 
are familiar to most people. All the species are of considerable size, and 
most of them are brightly coloured ; some, however, are of a bluish to 
purplish tinge. They are widely distributed and are common in most 
parts of the world. Calliphora erythrocephala, Macq., and C. vomitoria, 
L., are common American and British species ; the former is also found 
in North India. The larvae of C. vomitoria occasionally cause cutane- 
ous myiasis in man and animals. As a rule, however, the larvae of the 
Calliphora are useful scavengers, as they live by destroying animal refuse. 
The female flies are readily attracted to the bodies of dead animals, in 
which they deposit their eggs. Portschinski, who has studied the life 
history of C. erythrocephala in Russia, points out that the female lays 
from 450 to 600 eggs, 1 mm. in length ; in proportion to the size of the 
fly they are remarkably small. 

Genus Lucilia, Robineau-Desvoidy 

Medium-sized flies either green or bluish green. Posterior dorsocentral 
and acrostichal bristles constant and well developed. Sternopleural 
bristles arranged 2:1. Prothoracic stigmata black. Third longitudinal 
vein spinulose either at its base or throughout its length. 

The flies of this genus are distributed all over the world, but the 
species are most numerous in tropical countries. In order to collect 
them it is only necessary to place a piece of meat or the body of an 
animal in the open, or even in a room, when several females will alight 
on it and immediately lay their eggs. 

In South India Lucilia serenissima, Fabr., as a rule deposits its eggs 
in meat and in the dead bodies of animals, but occasionally it will 
oviposit in sores on the skin of sickly cattle ; this often occurs during 
outbreaks of ' Foot and Mouth ' disease in Madras. Lucilia caesar, L., 
a common European species, is also said to occasionally cause cutaneous 
myiasis by depositing its larvae in the skin of man and animals. 

Lucilia serenissima is a common bazaar-fly in South India, and 
feeds side by side with Musca nebulo on meat exposed for sale ; it is 



326 



MEDICAL ENTOMOLOGY 



nearly always infected with Herpetomonas liiciliae, Roubaud, and with 
Rhynchoidomonas hiciliae, Patton, which is parasitic in its Malpighian 
tubes. 

Genus Pycnosoma, Brauer and Bergenstamm 

Closely allied to Lucilia. Cheeks usually of a hujf or orange red. 
Posterior dorsocenfral and acrostichal bristles well developed. Sterno- 
pleural bristles only two in number, arranged 1 : 7. 

The flies of this genus are the Oriental representatives of the genus 
Chrysomyia, and are by some Dipterologists included with them. They 
are thick-set insects and have characteristic red cheeks. In tropical coun- 
tries they are abundant about night soil trenches and slaughter houses ; 
as they frequently alight on food they may be the disseminators of dis- 
ease-causing bacteria. Pycnosoma marginale Wied., is a common pest 
in the Soudan, and is widely distributed in Africa, being abundant in the 
Transvaal and Natal. Pynnosoma putorium, Wied., is common in West 
Africa, while P. flaviceps, Walk. , is common in South India. 

Genus Chrysomyia, Fabr. 

Medium-sized bright metallic flies, with three longitudinal stripes 
on the thorax. Thoracic bristles as a rule poorly developed and often 
inconstant. Sternopleural bristles three in number and arranged 2:1. 

The flies of this genus are restricted to America and the West Indies, 
and the best known, C. maceallria, Fabr., is the ' Screw Worm fly ', 
the larvae of which cause serious myiais in man and animals in 
Cuba, Brazil and other parts of Tropical America. The species are 
chiefly distinguished from Pycnosoma by the number and arrangement 
of the sternopleural bristles. 

Chrysomyia maceallria is of a metallic blue to green colour, with 
three black longitudinal stripes on the thorax ; the abdomen is covered 
with dark hairs. The legs are black and the wings transparent. It 
measures from 8 to 10 mm. in length. 

Its larva is of a dirty white colour and consists of twelve segments, 
each of which is furnished with one or more circlets of spines on its 
upper border ; the first has two, sometimes three, the second and third 
three each, and there are four on the other segments. The puparium is 
dark brown and has rudimentary spines. 

Chrysomyia macellaria will lay its eggs on an}- part of the body which 
has been injured, and is readily attracted to a bleeding surface. It will 



GENUS AUCHMEROMYIA 



327 



also oviposit in man's ears and nostrils, especially in those of people 

who have offensive discharges. Freire states that the female will also 

deposit its eggs in decomposing carcases. 

It is important for the worker to know exactly how to breed the Blow 

flies, for any of the species may act as a carrier of the bacteria of cholera, 

typhoid and dysentery. As in the case of the Sarco- 
, . , , . , 1 1 1 , r Breeding Techinque 

phagidae, some decaymg meat or the dead body oi a 

small animal should be placed in the open in order to attract the female 

flies, which may either be caught with a net or allowed to lay their eggs in 

body of the animal. Another simple way to obtain their eggs is to 

catch a number of flies round a filth trench, slaughter house or from 

stalls in the bazaar, and to place them in large test tubes, in which some 

of the gravid females will lay their eggs ; a small piece of meat placed 

at the bottom of the tube will tempt the flies to deposit their eggs. The 

meat containing the eggs, or the eggs themselves, should be transferred 

to a larger quantity of meat, which should then be placed in the mud 

enclosure (see page 314) as in the case of Sarcophaga. The larvae 

on hatching out grow rapidly, and when mature pass into the sand to 

pupate ; the puparia can be collected later and placed in the fly jars as 

described in the case of Musca. 

When the worker has a case of cutaneous myiasis to investigate, he 

should, as soon as possible, obtain several specimens of the living larvae 

and place them in some meat in the mud enclosure. 

On recovering the pupae he will be able to hatch 'dentif ication of 
. species causing 

out the fly, and will then be in a position to have it myiasis 

identified. This little experiment is frequently omitted, 
and instead, some of the larvae are preserved in alcohol, the observer 
being under the impression that the species can be determined by the 
examination of the larvae. At present practically nothing is known 
regarding the taxonomic characters of most of the larvae of the Callipho- 
rinae, and it is almost impossible b}^ examining the larvae alone to 
determine the species. 

Genus Auchmeromyia, Brauer and Bergenstamm 
Large broivnish yellowish flies. Cheeks broad and prominent. Last 
segment of the abdomen without prominent bristles. 

This genus contains the species A. liiteola, Fabr., the larva of which 
is known as the ' Congo Floor Maggot ', and which has the habit, unique 
amongst dipterous larvae, of sucking human blood. Although the fly 
has long been known to Dipterologists, it was not till 1904 that Dutton, 



328 



MEDICAL ENTOMOLOGY 



Todd and Christy made the discovery that its larva does not cause 
cutaneous myiasis, as was supposed, but actually sucks blood, behaving 
in the same way as the human tick, Oniithodonis inoiihata. The above 
observers saw the natives in the Congo collecting the larvae by digging 
with a knife, or scraping with a sharp stick, in cracks and crevices in the 
mud floors of their huts. It was noted that they always selected those 
huts the occupants of which slept on the floor, and that larvae were rare 
in huts where raised platforms or beds were used. The flies could be 
seen resting motionless on the grass walls, beams and other wooden 
supports of the huts, but as they are of a dusky colour, simulating their 
surroundings, they are apt to escape observation. The natives also stated 
that the female flies laid their eggs on the ground, choosing particularly 
those places where urine had been voided. 

Roubaud has recently made some observations, which are here 
summarized, on the habits of A. luteoJa. The adult fly always shuns 
light and is almost invariablj- found in the darkest 
A luteola parts of the native huts ; it is very sensitive to heat 

and dies in the sun or when exposed to a temperature 
of 45° C. Roubaud states that all the species of Aiichmeromyia are blood- 
feeders in their adult stages ; they can, however, be kept alive for long 
periods on sweet liquids, but then never oviposit. In captivity A. luteola 
has two periods of oviposition, separated by about a month ; a single fly 
has laid as many as eight-three eggs, the majority of which were 
deposited during the first period. 

The larvae are exclusively blood-feeders, and have never been known 
to take any other food ; they are able to resist starvation for long periods, 
the young larvae for three weeks, the older ones for a month or more. 
If fed daily their period of growth occupies about fifteen days ; they 
moult twice, once about the second and again about the sixth day. 

When buried in the earth thej^ exhibit a remarkable sensibility to heat, 
becoming very active when the soil is warmed. Roubaud thinks it is this 
thermotropism which guides them to their hosts ; they appear only to be 
sensitive to heat when starving, and when fed do not respond to any rise 
of temperature. 

Button, Todd and Christy give a good account of the larva and 
its anatomy. The larva is semi-translucent, of a dirt}' white colour, 
acephalous and amphipneustic, and consists of seven 
Structure^of the segments. The first is divided by a constriction into 
two portions, the most anterior of which bears the 
mouth parts, and is capable of protrusion and retraction. At the 



AUCHMEROMYIA LUTEOLA 



329 



junction of the dorsal and ventral surfaces of the larva there is a 
row of irregular protuberances on each of which there is a small pit 
and a posteriori)' directed spine. At the posterior margin of each 
segment there is a set of three foot-pads, each covered with small 
backwardly directed spines, which aid the creature in its movements. 
The last segment is larger than the others, and bears the posterior 
spiracles, which are seen as three brown transverse, parallel lines. The 
two black mandibles protrude from the anterior segment, and are 
curved towards the ventral side. There are paired groups of minute 
spicular teeth around the mandibles, forming a sort of cupping 
instrument. 

The intestinal canal commences as a short oesophagus, which ends in 
a proventriculus. A dorsal diverticulum, the food reservoir, opens into 
the oesophagus near its anterior end, and when the larva is replete with 
blood it is seen as a bright red area extending from the head to the fifth 
segment. The mid-gut is short, extending from the proventriculus to the 
junction of the Malpighian tubes with the gut. The- hind-gut is con- 
siderably coiled, and occupies the greater part of the body cavity. There 
are two Malpighian tubes, each of which is divided into two branches. 
There are two salivary glands, each of which consists of a long acinus 
made up of large granular cells. Each gland ends in a ringed chitinous 
duct which unites with its fellow of the opposite side to form a common 
duct, the opening of which is situated near the base of the free portion 
of the mandible. 

The piipariiiin of A. hiteola is of the usual muscid type, and of a dark 
brown colour. The fly is the size of a blue bottle, but is of a tawny 
colovir ; the dorsal surface of the thorax is marked by black and brown 
stripes. The abdomen is characteristically marked, and has unequal 
segments. In the male the second segment is about one-third longer 
than the third, and has a black median longitudinal stripe, and another 
meeting it at right angles at the posterior border. In the female the 
second segment is two-thirds longer than the third. The legs are of 
a buff colour, but the first tarsal joint is black. The fly is found from 
Nigeria to Natal. 

In a recent paper Rodhain and Bequaert state that A. hiteola is 
widely distributed in the Belgian Congo and occurs all the year 
round. The fly probably spreads from one village to another, either in 
the egg or larval stage, in the dirty mats which the natives carry 
about with them. The fly will appear in newly constructed huts in 
about three weeks time. 
42 



330 



MEDICAL ENTOMOLOGY 



Genus Choeromyia, Roubaud 

Allied to Auchmeroinyla : the abdomen is shorter, more tapering and 
has equal segments. 

This genus, which has been created recently by Roubaud, contains 
two species whose larvae suck the blood of wart hogs and Aard-varks in 
the Soudan. Choeromyia boiieti, Roubaud, is found in Niamey and 
Timbuctoo, where its larvae live in or near the lairs of the Aard-vark, 
Orcteropiis senegalensis, Lese., and the wart hog, Phacochaeriis africana, 
Cuv. The larvae of C. houeti resemble those of A. liiteola and live in 
the damp earth in or near the lairs of these animals ; the larval stage 
lasts fifteen daj's, and the pupal stage about eleven. The fly lays about 
fifty eggs, all in a heap, in the sand. The larvae are voracious blood- 
suckers, and can ingest about three times their weight of blood. Their 
biting apparatus appears to be similar to that of A. liiteola. 

C. choerophaga, Roubaud, is an allied species whose larvae feed on the 
wart hog. 

Genus Ochromyia, Macquart 

The flies of this genus are the nearest oriental allies to Atichmeromyia ; 
with which some dipterologists group them. O. jejune is a common 
Indian species, and is usually to be seen resting on walls in Madras. It 
is said to feed on termites when they swarm. Howlett records having 
seen this fly catching ants while carrying their eggs or nymphs, and 
dragging the latter away from them, and sucking out their juices. 

Genus Bengalia, Robineau-Desvoidy 

Large yellowish flies. Cheehs narrow. Last segment of abdomen with 
prominent bristles. 

Several species of Bengalia are known, B. depressa being the com- 
monest ; it is a maggot fly and causes myiasis in man and animals in 
many parts of Africa. According to Mennel it is widely distributed in 
Rhodesia, but it also ranges into British Central Africa, and Uganda. 
It is a large fly of a yellowish brown colour, with two dusky bands near 
the apex of the abdomen. Mennel states that it deposits its eggs on the 
hairs of animals, and on clothing, especially when hung out to dry. 
Fuller, on the other hand, thinks that the fly deposits its eggs chiefly on 
the scalp, in which situation he has seen twenty to thirty maggots. 
The larvae always leave their host and pupate in the ground. 



SUBFAMILY MUSCINAE 331 

Genus Cordylobia, Grunberg 

Large broicnisli ydloic flics rcseiiib/iiig Aiic/iiiicroniyia. Front in male 
narrow. Abdomen rounded and not elongate. 

Three species of this essentially African genus are known, one of which 
is the 'Thumbu fi}- C. anfJiropophaga, Grunberg, which in its larval 
stage (' cayor maggot ') causes cutaneous myiasis in man and animals. This 
fly resembles A. luteola, but can be distinguished by the narrow front in 
the male and the rounded abdomen. Nothing is definitely known as to 
how the larvae of anthropophaga gain access to the human skin. Each 
larva forms a large swelling in the skin which has a central opening 
through which it breathes ; like B. depressa, it drops out when mature, 
and pupates in the ground. 

Rhodain and Bequaert have recently studied the habits of this lly in 
Katanga. They record the occurrence of cutaneous myiasis caused by its 
larvae in dogs, rabbits and goats ; the larvae are nearly alwaj s found in 
the scrotum of the animals. Several cases of human cutaneous myiasis 
were also seen. These observers believe the fly lays its eggs on the ground 
in places where there is a smell of human or animal perspiration, as the 
tumours containing the larvae are alwa} s seen in parts of the body ^^ hich 
come in contact with the ground. In the case of man the fly sometimes 
lays its eggs on clothes which are saturated with perspiration. 

THE MUSCINAE 

Small to niedinni-sized flies of a dark grey to black colour, rarely 
metallic. Eyes bare or pubescent. Arista either bare or plumose, some- 
times pectinate. Front narrow in the male. Thorax of a grey to black 
colour commonly marked with tico or more dark longitudinal bands. 
Sternopleural bristles varying in number and arranged 0 : 2 ; 1:2; 1:3 
or 2 : 2. Venation of the muscid type. Last section of fourth vein 
either with a broad curvature about its middle, with a sharp or rounded 
angle, or curving forwards slightly beyond its middle ; first posterior 
cell either closed or widely open. 

In the subfamily Muscinae are included the non-biting Muscidae, of which 
there are about twelve genera. The imagines are common everywhere 
and exhibit varying habits. A few are true domestic insects {Musca and 
Muscina), and are common in and about dwelling houses and stables ; 
the majorit}-, however, are wild insects (Morellia, Pyrellia, etc.) The 
house flies (Musca), on account of their habits, have attracted the most 



332 



MEDICAL ENTOMOLOGY 



attention ; they are dealt with fully further on. Several species of 
' Morellia occasionally come into houses ; they can be recognized by 
their dark bluish colour and by the two broad dark bands on the thorax. 
Their larvae are very characteristic ; they are short and have a disc-like 
posterior extremity on which are situated the posterior stigmata. In 
North America, Morellia inicans, Macq., breeds almost entirely in human 
excrement. In Madras, Morellia Jiortensia, Stein, breeds in cow dung ; 
its eggs are laid singly, and have a short curved spine. The imagines are 
often seen on cattle, sucking up the juices which exude from wounds and 
bites inflicted by biting flies. It is interesting to note that this species 
and another from Kodaikanal, South India, have somewhat strongly 
developed prestomal teeth. 

Mttsciiia stabnlaiis, a common stable fl\-, is found throughout Europe and 
North America ; it breeds in dung, and in decaying animal and vegetable 
matter. The species of Pyrellia and Pseiidopyrellia usually breed in 
cow dung, though some of the former oviposit in the bodies of animals. 

Genus Musca, L. 

Small or moderately large insects of a greyish to dull black colour, 
but never metallic. The eyes in the male are contiguous or nearly so, 
the frons being about one-fifth the total xvidth of the head ; in the 
female they are widely separated, the frons being about one-third the total 
■width of the head. The palpi are cylindrical, and slightly narroived 
towards their bases. The proboscis is retractile and can be tucked aii\iy 
under the head, the usual position ichen the fly is not feeding. The 
thorax is nearly ahvays marked icith four narroic to broad longitudinal 
stripes though sometimes there are only tico. Thoracic chaetotaxy 
{macrochaetae) as folloics .-—Humeral, 3; post-humeral, I ; notopleural, 2; 
presutural, I ; supra-alar, I ; intra-alar, I ; post-alar, 3 ; dorsocentral, 6 
to 8, two to three in front of the suture and three to four behind it; 
acrostichal I to 3 ; mesopleural 6, the distance between the first and 
second being much greater than that between any other two; the first 
bristle is nearly always bent upwards ; sternopleural bristles 3, arranged 
1 : 2: pteropleural bristles wanting. Wings hyaline, yellowish at the 
border; fourth posterior vein bending up at a sharp angle, and first 
posterior cell almost closed. Reproduction nearly always oviparous, but 
may be larviparous. Larva cylindrical, posterior stigmata large and 
xcidely separated, stigmal slits narrow and coiled: puparium yellowish 
white or olive grey to mahogany brown. 



MUSCA DOiMESTICA 



333 



For practical purposes the genus Musca may be divided into two 
groups as follows : — 

Group 1. The non-blood-sucking species, including all the house 
flies. 

Group 2. The non-biting, blood-sucking species, including tliose 
wild forms closely resembling Musca domestica. 

Group 1. The Non-blood-sucking Species of Musca 

To this group belong those species of Musca which are domestic in- 
sects, living on all kinds of human and animal food, and on filth and 
garbage of every description. They come into houses and settle on food, 
cooked or uncooked, and on being driven away seek nourishment either 
from horse manure, cow dung or human excrement. They worry man 
especially when he has sores or foul discharges, and the reader if he has 
been in an Indian or African bazaar will recall the swarms of flies 
buzzing round some food or the sore eyes of a child. These insects 
are a constant source of danger to man, for they not only infect his 
person with bacteria, but certainly contaminate his food. 

The true Musca domestica is found in most parts of the world. 
It is said to occur in North India, but is not to be found in South 
India. There is, however, no accurate information on this point, and 
this is perhaps mainly due to the fact that there are no simple complete 
descriptions of the group available for general use ; the result is that 
most observers who have studied the species of Musca in their relations 
to disease germs have simply spoken of them as house flies ; to the 
zoologist this term only refers to the species Musca domestica, L. 
It is of some importance to know exactly which species is being dealt 
with, as those which only breed in cow dung or the refuse around 
slaughter houses are not of so much importance as those which breed in 
human excrement. 

The following short descriptions of Musca domestica and some of 
its allies will help the worker to identify his species. 

Musca domestica, L. Male- Thorax, ground colour yellowish grey 
to dark grey, with four equally broad black longitudinal stripes ; shoul- 
ders slate grey ; scutellum dark grey with an indistinct broad central 
band. First to third segments of abdomen orange yellow with a median 
black longitudinal stripe, broadest on the third segment. Fourth seg- 
ment with an indistinct diffuse olive grey patch about the centre, sides 
lemon yellow. In certain lights a shimmering white band is seen on 



334 



MEDICAL ENTOMOLOGY 



either side of the central black stripe on the third segment, and a similar 
* white patch at the sides of the second and third segments. Length 
5'8 to 6'5 mm. 

Female (Plate XLIII, fig. 1). Ground colour lighter than the male. 
Thorax yellowish grey, with four dark bands similar to those in the 
male ; scutellum olive grey. Abdomen lemon yellow with darker patches ; 
first segment with a central black longitudinal stripe. Second segment 
also with a central stripe, and two somewhat indistinct triangular brown 
bands at the sides; the intervening areas are silvery grey and rectangular 
in shape. Third segment with markings very similar to those of the 
second, the lateral bands narrower and pointed towards their anterior 
ends ; fourth segment olive grey, with two narrow converging lateral 
brown bands. Length 6'5 to 7'5 mm. 

Miisca nebula, Fabr. Male. Thorax, ground colour dark grey to 
bluish grey with four black longitudinal stripes ; scutellum dark gre}'. 
Abdomen j-ellowish throughout with a somewhat narrow black central 
longitudinal stripe ; fourth segment with a small indistinct olive grey 
patch at its centre. Length 5 to 5'5 mm. 

Taken as a whole the male iiebiilo is considerably smaller and darker 
than the male doinestica ; the thoracic bands are narrower, and the 
fourth abdominal segment is much lighter in colour. 

Female (Plate XLIH, fig. 2). Thorax, ground colour yellowish grey, 
with four clove brown longitudinal stripes ; scutellum light grey. 
Abdomen yellow, with a black median longitudinal stripe on the second 
and third segments, and an incomplete stripe on the first and fourth ; 
lateral borders of second and third segments \\ ith a faint brown stripe, 
and shimmering patches at the sides. Length 5 to 6 mm. 

Miisca nebula is the common house fly of South India, and breeds 
in night soil trenches, but can be easily reared in horse dung, and in the 
contents of the intestines of goats, which are to be found collected outside 
slaughter houses in India. Its puparium is of a dark mahoganj- colour. 
It is probabl}- much more widely distributed in India than is at present 
believed ; it occurs in Bombay, and in parts of Gujarat. 

Musca sp. incert. Male. F"rons very narrow, much narrower than 
that of the male nebula. Thorax, ground colour dark grey to bluish grey, 
w ith four black longitudinal stripes, broader than those of nebula ; scu- 
lellum black in the centre, and greyish at the sides. Abdomen dark 
orange with a broad black central longitudinal stripe on the second to 
the fourth segments inclusive, narrowest on the last ; on each side of 
this median band there is a well-defined silver)- stripe, and two similar 




334 



Fig. 2. Musca nebulo, $ . x 10. 



DOMESTIC SPECIES OF MUSCA 



335 



white patches at the lateral borders of the segments. Length 5 "6 to 
6"5 mm. 

Female. Yellow ish to olive grey, and quite unlike the male. Thorax, 
ground colour yellowish gre\-, sometimes appearing silvery grey, w ith the 
usual four longitudinal stripes ; scutellum olive grey. Abdomen olive 
green with a general chequered appearance ; first segment brownish grey 
in the centre, and olive grey at the sides, with a somewhat diffuse dark 
brown central longitudinal stripe, and with rectangular shimmering white 
bands at each side, and an indistinct lateral brown band ; third segment 
with markings similar to those of the second, except that the central 
black band does not reach the lower border ; fourth segment with an olive 
grey central patch ; all the segments except the first have white borders. 

After due consideration, it has been decided for the present to leave 
this species of Miisca unnamed, as it is not possible to sa\' whether it 
has already been described or not. It is a common house fly in Madras, 
and has also been seen in Bombay and Gujarat. It usually breeds in 
the refuse arovmd Indian slaughter houses, and in horse dung; in 
Bombay large numbers of its larvae were found in a garden in rose pots 
which had been filled with horse manure. 

This Miisca can be distinguished from the other Indian species by 
the narrow front in the male and by the characteristic lateral silvery 
band on the abdomen. It is very difficult to distinguish the female from 
that of nebiilo. 

Miisca enfeniata, Bigot. Hewitt gives the following translation of 
Bigot's description of this species : — ' Front very narrow, the eyes 
' however separated. Antennae and palpi black ; face and cheeks white ; 
' thorax black with three broad grey longitudinal bands ; sides grey ; scu- 
* tellum black with two similar grey bands ; halteres of a pale yellowish 
' colour; abdomen fawn coloured, with a dorsal black band, and sometimes 
' with light patches ; legs black ; wings hyaline ; fourth long vein turning 
' up at a slightly rounded angle, then becoming a little concave ; second 
' transverse vein (extreme) nearly perpendicular, and with two slight 
' sinuosities, joining the fourth vein at an equal distance from the bend 
' and the first transverse vein. Length 4 to 5 mm.' 

The above description is very inadequate and would apply equally- 
well to nehiilo. After comparing some specimens from the Indian 
Museum, provisionally named enteniafa by Dr. Annandale, with many 
specimens of nehtilo it was found that no reliable distinguishing characters 
could be detected between the two. It is very probable that one or other 
of these names will in time have to be dropped. 



336 



MEDICAL ENTOMOLOGY 



Smith records enteniata from Benares, the specimens being identified 
by Austen, and states that it breeds in human excrement, and in cow 
dung cakes. It is also said to occur in Suez, Aden (Hewitt), and Khar- 
toum (Balfour). 

Musca doinestica, sub-species detenninata, Walker. This species, from 
the East Indies, is described by Walker as follows: — 'Black, with a 
' hoary covering ; frontalia broad, black, narrower towards the feelers ; 
' eyes bare; palpi and feelers black; chest with four black stripes ; abdomen 
' cinerous, with a large tawny spot on each side at the base ; legs black ; 
' wings slightly grey, with a tawny tinge at the base; prebrachialvein (fourth 
' longitudinal) forming a very obtuse angle at its flexure, very slightly 
' bent inward from thence 'to the tip ; lower cross-vein almost straight ; 
' alulae whitish, with pale yellow borders ; halteres tawny.' 

Aldridge states that at certain seasons in Meerut it is present in enor- 
mous numbers, and Dwyer records it from Mhow. Smith found this 
species in a militar}- hospital ward at Benares. It is also said to occur 
in Deesa, and in the Kangra valley ; Hewitt records it from Aden. It 
breeds in